You’ve probably seen that there is a lot of repair info and cleaning tips on individual camera & lens pages where I’ve had to do some minor work. Here is where you’ll find general camera repair and cleaning info, and info on repairing and cleaning specific cameras and lenses like the Yashica GSN and the Industar-61 that became extensive enough to warrant their own pages. Over the years I’ve gotten more questions about the Yashica GSN and I have to say, if it’s not on that page, I probably don’t know!
In general, your best place to get parts is from a broken ‘parts’ camera that is identical or near identical to the one you’re trying to fix, and which you can usually get pretty cheap. I don’t actively repair cameras any longer so these pages aren’t getting updated, but they should help you on your way to being your own Mr or Ms Fixit!
There’s also a page on buying cameras on eBay that’s as true as when I wrote it years ago.