This thread has inspired me to resume work on my cheap/broken 500c outfit. I had previously brought an old chrome 120 S-Planar lens back to life, and now it's time for me to tackle the 500c camera body, WLF and A12 film back. I have worked on a 500c before, but have gone into much more depth this time, going so far as to remove the mirror and replace the foam behind it, as it had crumbled away long ago. For general servicing not including the mirror, I got some help from the following series of videos, although technician Jim mostly skips particulars about re-installation of a pair of springs for the mirror, and even with the service manual, it took some time for me to figure out how to proceed. Hope to complete mechanical work on the 500c body within the next few days.
Lessons learned so far: If a procedure seems especially difficult, it's probably because it's not being done the way the factory anticipated!
The first installment of the videos in question:
https://www.youtube.com/watch?v=vOFdK7ySkj4&t=719s