The door chime is barely audible

You're stuck with the dealer on this one. Beginning with the '94 model year GM stopped allowing us to buy radio service manuals because they wanted to lock up all the repair business for their two grossly over-priced repair centers. Starting with some 2002 models they built the Body Computer into the radio so you had to get it fixed instead of buying an aftermarket replacement. Repaired / replaced radios also have to be programmed to the vehicle so the dealer can charge even more money from unsuspecting owners. This is just one of many reasons GM is having trouble finding repeat customers.