As far as having to readjust the RD; most likely you'll need to adjust the "B" adjuster. The H and L stops should be okay. You'll need to lengthen the chain, so it might be a good idea to replace it at this time. I have a 2005 Trek 2100 too. It's been pretty good except that the rear Race wheel rim cracked. Trek replaced it, no questions asked. Everything else has been perfect.