Ok, I took my beloved Gary Fisher Advance to the LBS for a tuneup. I expected a few things: a new cable or two, chain and rear cassette due to wear, and the seatpost freed up. I wound up with all new cables (fine), new RD (well, used; but maybe it was in better shape than my old Alivio), new "pods" for both front and rear stuff (the RD shifter was shot, and the front brake lever was very loose, so ok), Acera level. I had requested new grips and new pedals. But the chain and rear gears were untouched.
Wasn't until I was halfway home that I remembered why I really wanted a new chain: last time I was out trail riding, I snapped the chain. [I'm sure it's a link short now, as we put it back together and I rode it out.] Now, I recall, either on this chain or the last, taking it off and blasting it with some chain cleaner: so it is possible that I had a loose link (Shimano everything on the bike) and that is what gave out. But a quick look at home, with a ruler, shows about 1/8th of an inch of chain stretch. Also, the granny gear on the cassette (and the next few too) show some serious wear--the granny gear actually has a ridge forming, from the metal bending down!
I also think the BB may be a bit loose; while pedaling, I get grinding on the FD--but only in certain foot positions. I don't feel that much play in the BB, but I think it's worse in certain crankarm positions than others. Maybe the chainring is bent.
Anyhow, on the good side I didn't pay too much. On the bad side, I don't think my bike is in good enough condition for trail riding. I'm sure they can true rims better than me, but I think I might just start doing this work myself, starting with a new drivetrain.