Re: 475 questions
It sounds as if your philosophy of whether to keep or replace suspect components matches mine. My understanding of what each component is doing in a particular circuit is very weak, so I'm not sure what a suitable replacement would be if not the identical part, and these boards were manufactured in late 1982, so it's not exactly current technology. That can be a good thing, because it was intended to be maintainable, rather than tossing an entire board or worse, an entire device, when something goes bad. So, as several have suggested, I keep asking questions! I try to do my own research, too, but sometimes the explanations on websites are over my head or don't match my question closely enough. You guys have been much better in that respect!
I agree that I shouldn't be trying further diagnosis until my power rails are up and in spec. But when I poke around and see out-of-spec components on a relatively inaccessible board, I'm inclined to replace them if I can figure out what they should be replaced with.
I haven't commented on the attachments debate, but I'm with you for allowing them. There is https://groups.io/g/TekScopes/photos. Is that a good place for me to post?