I picked up a 1989 1200 cheap, haven't done much with it yet but planning on riding it a fair deal soon. It came with a full 105 groupo. 1990 1200 when a bit cheaper on components. It has downtube shifters but I have a spare right brifter I will throw on there.

The aluminum frames were bonded (epoxy/glue) instead of welded, and the in-house wheel brand (Matrix) had a pretty bad rap.

I don't know when they changed, but mine has a 126mm rear axle width. Some people discourage stretching the rear triangle to accept standard 130mm axles. (I still have the original)

I would recommend getting one with brifters unless you want to keep the downtube shifters or have spare brifters. Upgrading can be expensive.

I'm not an expert by any means, but I like the one I got.

http://www.vintage-trek.com/
This site has a lot of info and while geared at some of the older Treks, it has links to more current model data