tjspiel

You may ultimately want to get a new bike but since I like working on old things and don't like to sell something that's not working right, I'd be inclined to fix the old bike regardless.

I wouldn't buy new parts though unless you're just going to replace the jockey wheels and not the whole derailleur. If you don't have a bike shop in your area with a "salvage yard", post a "wanted" add on your local craigslist. No need to wait until someone posts something you're looking for. Go ahead and ask. Post wanted adds in neighboring cities as well.

And there is always Ebay.

As far as what to fix, you may not need a bottom bracket at all unless the races are shot. I have an '86 Univega and the BB started to creak. I just pulled it apart, replaced the bearings and along with the bearings put grease on every metal to metal contact point, - like the face of the BB shell. I also removed the chain rings and greased the bolts. When I put it all back together the creaking was gone. Creaks from that area can also be from the pedals so be sure to lightly grease the face of the crank arms near the pedal threads.

You could really have some fun and upgrade to indexed shifting. You'd need new cables, shifters and a hyperglide freewheel along with the derailleurs. But all that (aside from the cables) can be found used pretty cheap. Get new cables.

You could also go the other direction. Any desire to try a fixed gear? Now's a great opportunity. I confess to being a fixie skeptic a few years ago, but now I'm fairly enamored with them. I'm not saying you've got to saw off all the cable guides and everything. Leave those in place in case you want to convert it back.