Sounds like a nice old tractor. Old tractors can be jewels. They were built to last and to be owner serviced and repaired. It could easily last a lifetime.
All 3 pt attachments and almost all PTOs will fit since those are standard size. Many typical service parts including seats, most of the electrics, instruments, tires, hoses etc. are of course all standard.
Anything else external is easy enough for a person with basic mechanical skills to fabricate. Internal engine and transmission repair is very rarely ever needed, even on much older machines.
See if you can get an original factory owners manual and also workshop and parts manuals. Expect the workshop & parts manuals to be expensive but worth it.
From your description of that
B7500, I doubt you will do better even if you go up substantially on price.
rScotty