Nice bike. I owned one from '88 or '89 'til '98 when I broke the frame at the rear of the chainstay. It took an awful lot of abuse.

This link is to a fella that has his all decked out. You may find it useful: http://www.thirdwave-websites.com/bike/trek830.cfm

I think you'll be able to fit most any standard rack. Nothing unusual about an 830—a fine bike.