I think you will find this link helpful: http://ls1tech.com/forums/new-ls1-ow...questions.html
Contained within is a list of all the little differences between the model years, and a lot of basic info about these cars in general.
There is somewhat of an internet myth that the later models are vastly superior to the earlier models, and/or that their differences are exclusively improvements. My perspective on this, after personally owning a '98, '99, '00, and '02, is that this is untrue. There are certainly some small differences, and your personal goals and preferences will dictate how positive or negative or significant these differences actually are, but in general you will be best served to buy the nicest condition example you can find that offers the options that matter most to you (trim level, roof type, trans type, color, etc.) regardless of model year.