Thanks for the welcomes!
My riding is over for now. As I left my house for my last ride, the chain came off - I didn't think much of it & reinstalled the chain. After this incident the chain was noisy & wouldn't shift so I headed back home for inspection. The cable-end for the rear shifter somehow came out of it's normal position & wedged itself inside into the (right-side) shifter assembly - the cable didn't break, but rather folded over itself & did a nice job of wedging everything into an unreachable spot.
I've always been a DIY guy, so without thinking I started taking apart the rear shift lever to get to the cable end... When I heard the spring come loose I knew I'd made a mistake (how am I going to get this spring retensioned?). There was no amout of disassembly that would've got me to the stuck pieces AND now I've got a busted shifter. I made a tool to help get the spring back into position, but it seems like the shifter needs more spring tension than I've been able to give it.
The bike is now at the bike shop but they don't think they'll be able to fix it since I've sprung the spring.
I'm now looking at a $200 repair (my guess based on their $150 estimate for a new shifter) - so much for saving money by buying a used bike. I've got no idea how long it'll take them to get the new part in. They say they've seen this before (the cable issue) & that it's not an unheard of problem for Shimano components - I've got Tigara shifters with 105 derailers.
Wishing I'd gone to Walmart instead of Craigslist
