I am the original owner of this bike, black frame with red letters and white seat. Even though my beater mountain bikes have come and go, I still just love the ride of this old sport touring machine and I simply cannot part with it. But just like my 52 year-old knees she is beginning to show her age, and I would really appreciate some advice on renovation upgrades. So if you have the knowledge and and can share it I would be very grateful.

Specifically:
1. I have the basic 12 speed model with Sugino cranks and two front chainrings + six gears in back. I don't know if it's freewheel or cassette-- whazzat? Derailleurs and shifts are all Suntour. I would like to upgrade to 3 chainrings in front to help on the hills, and to replace the Suntour downtube shifters with something higher up on my flat handle bars. What should I look for on a donor bike? Are there new parts I should consider?

2. The bottom bracket is now showing the slightest wobble... How do I find out the necessary information to overhaul or replace it? Is this worth the energy?

3. Any suggestions for getting a better wheel in back-- the cheap 27 rims that the LBS have been putting on only last a few years before the spokes start to rot, even though my front wheel is original and A-ok. I'm fine to switch to 700c if there is a suitable donor, or to build a new rear wheel if needed. But I am clueless about what hub will fit in a 126mm dropout space and what cassette I can use to match the rest of the upgrade that I want to do. Where do I even start? C-l-u-e-l-e-s-s.

4. Last and actually least important, an LBS guy once told me my fork is slightly bent. It would be nice to put something newer up there if that is practical. I have heard of people switching to threadless headsets but i don't fully understand the pros and cons.

Many thanks for any advice!!