I've been doing some of the repairs myself but today's problem needed special tools to take apart the rear end so it went to the shop. I also don't seem to have a handle on adjusting the shifter.
I've replaced all the drive components except the derailleur and front sprokets. the derailleur that's on the bike is bottom of the line and the spring is weak.
I trust the guys at the local shop, they only charge $20 an hour for labor, and that ain't much. I talked to the owner today about buying a new bike and he said just keep upgrading the parts as they break, probably a good idea.