Well, I know just enough on the topic to have this sort of work done by an expert. There's a handful of guys around the country who specialize in rebuilding vintage audio gear but the ones I know of having a waiting list sometimes 3+ years deep.
The gear from the 50's, 60's and early 70's is very well made and much more robust to the stuff made now, but as you know nothing last forever. The good news is the bad or obsolete bits can be replaced (by someone who understands such stuff) and these old warriors can live on for several more decades.