1) You've referred to eschatology as a personal hobby, but many people seem to view it as a fundamental issue that determines salvation. What does a healthy Christian understanding of eschatology look like? How much of our time and study should we devote to it?

Well, eschatology is not so much a hobby for me as a professional interest–an interest I've had for some time, however.  No, one's eschatology does not determine where they will spend eternity–their relationship to Jesus Christ does.  But since the Bible (especially the New Testament) says a great deal about eschatology, I tend not to be very sympathetic toward those who call themselves "pan-millennarians" and who adopt no particular eschatological position, lamely claiming that "things will pan out in the end."  Of course, things will work out according to God's plan and purpose, but since eschatology is an important part of biblical teaching, Christians are obligated to make some effort to read and study eschatological matters, just as they should do in other areas of Christian doctrine.  Yes, eschatology can be a complicated, confusing, and difficult subject.  But sloth or indifference toward the subject are not options! 

So, while our millennial position does not determine our salvation, identifying the underlying hermeneutic we use to interpret Scripture and then realizing how this hermeneutic will impact our reading of the Bible is a very important matter.  Not only does our hermeneutic color how understand those passages which deal with end-times, our hermeneutic also influences how we understand and work out the ramifications of matters related to our salvation.  There is a certain inter-connectedness here. 

We all have hermeneutical assumptions, which we need to identify and continually re-evaluate in the light of Scripture.  Things get dicey when people assume that their eschatological views just jump out from the pages of Scripture, as though the Bible taught dispensationalism or covenant theology, just as we find it taught among our contemporaries.  What I'm getting at is that if you are a dispensationalist, you need to identify your operating assumptions–two redemptive purposes, one for national Israel, one for believing Gentiles, and the so-called "literal" interpretation of the Bible.  On the amillennial side, we believe that covenant theology is Scripture's own internal architecture and that the authors of the New Testament tell us that Jesus Christ (not Israel) is the hermeneutical center of all of Scripture.  Unless we keep these presuppositions before us, and unless we are willing to continually evaluate them in the light of Scripture, as well as in light of the arguments raised against us by those who happen to disagree, all we can do is shout at each other or extend pointless anathemas.

We need to be clear that our eschatology does have an impact on a number of doctrines.  Take for example the kingship of Christ (part of his three-fold office as prophet, priest and king).  Dispensationalists tell us that the kingdom offer was withdrawn when Jesus appeared in Israel and was rejected by the Jews, and that his kingdom will not be fully manifest until the millennial age.  But Reformed amillennarians (such as myself) see Christ' kingdom as a present reality (through word and sacrament) and that Christ's kingship (his present rule before the final consummation) not only ensures the victory of his kingdom in this present evil age, but his present rule (through the indwelling Holy Spirit) is one of the primary factors in my sanctification as Christ's rule breaks the power of sin which one held sway over his people (mortification and vivification).  That's why you'll see Reformed amillennarians speak often of eschatology (although not in the ways in which dispensationalists do), since we tend not to push things off into the future.  Rather, we see much of the New Testament's teaching on eschatology as a present reality and as having a direct impact upon many aspects of the Christian life.  

2)  So far, you've published two books on eschatology, the first being A Case for Amillennialism. I remember first hearing about this view (in my less-educated dispensational days) and being told it meant there is no millennium. Could you clarify in a nutshell what amillennialism is for those who may have similar misunderstandings?

Amillennialism is simply the view that what is depicted in Revelation 20:1-10 is a description of the period of time between the first coming of Christ (and his binding of Satan) and his second coming (when the beast and the false prophet are cast into the lake of fire).  The scene in the first 6 verses of Revelation 20 take place in heaven and not on earth (that's where the thrones are).  The thousand years are a figurative period of time–numbers in Revelation are always used symbolically.  The first resurrection is a believer's conversion (John 5:24-25), and those who experience the first resurrection need not fear the second death.  When we speak of amillennialism, we really mean "present millennialism."  We do not "spiritualize" the Bible as dispensationalists claim.  Neither do we hold to "replacement theology," but that is another discussion for another time.

3) Since you brought it up, I'm always baffled when the "replacement theology" charge is made against covenant theology. We hold that God has always had one way of saving his people, yet dispensationalists believe God has had at least two different plans for redemption. Doesn't that make dispensationalism the real "replacement theology"?

I too am baffled by the charge, because I don’t know of any current amillennial writers who speak of the church as “replacing Israel.”  As you point out, God will save his elect.  There is only one gospel throughout both testaments--Romans 4 comes to mind here.
 
In the Old Testament, the elect (those who are truly members of the covenant of grace–who believed the promise as did Abraham) were almost exclusively Israelites.  But you also have people like Melchizadek, who is a type of Christ, and to whom Abraham pays tithes.  When Jonah preaches in Nineveh, we read that many repented (Jonah 3:6-10).  When Israel entered Canaan, the Gibeonites tricked Joshua so as to be included in the covenant with YHWH (Joshua 9).  Presumably there were elect believers in Nineveh and among the Gibeonites, who were outside the boundary of national Israel and who somehow believed YHWH would save them from their sins.  It is important to notice that as the gospel spreads from Jerusalem to the ends of the earth (Acts 1:8), the focus dramatically shifts to elect Gentiles coming to faith.  That said, I do believe that in Romans 9-11, Paul teaches that immediately before the end of the age vast numbers of ethnic Jews will come to faith in Christ and join Christ’s church.

When Jesus began his messianic ministry, he started with twelve disciples and a few additional followers.  By the time of his death and resurrection, there are still relatively few believers in Israel outside the apostolic circle (Nicodemus, comes to mind).  After Pentecost, thousands more come to faith–primarily Jews initially, but then we see an increasing number of Gentiles embracing Israel’s Messiah.  So, it is not as though the church “replaces” Israel.  Rather, Christ is the true Israel, and when he comes, he adds a gazillion Gentiles (who are elect) to his church.  To speak of amillennialism as though we reject Israel on some sort of racial basis–thereby opening the door to anti-Semitism–is a sad case of a straw-man argument.  A while back, I responded to a recent lecture given by John MacArthur on this very subject.  Your readers might find it helpful.  http://kimriddlebarger.squarespace.com/a-reply-to-john-macarthur/

And yes, you are absolutely right.  It is ironic that the dispensationalists divide what Christ has joined together (Ephesians 2:11-22) by emphasizing different redemptive programs for Jew and Gentile.  This “replaces” the one gospel which has one purpose (to make Jew and Gentile one), with one gospel with two purposes (one for Jew and one for Gentile).  Ironically, this separates the very people (Jew and Gentile) Christ came to join together into one body.