My SD has a pop in the steering. That turned out to be upper ball joints. Parts were $400 and didn't include tie rods or guide rods. I could have saved a little perhaps $100 by going with cheaper parts.

I need to find time and a spring compressor before tackling the job.

Don't guess at suspension parts. At least take it to one on the McQuick alignment places & get their list of what needs to be done. Given your stated wrenching skills, I'd expect your car to be down for a while while you learn suspension work.

Over heating is not difficult. Perhaps thermostat or radiator needing a flush or replacement. It sounds like you need to change the coolant anyway. You will get electrolysis started which will eat your heater core if you don't change the coolant. NAPA has full strength Zerex G-05.

Shut off is likely vacuum leaks. You can plug the dash/climate control vac lines to test. Your vacuum locks don't work so plug those also.

There are vacuum diagrams available for all interior systems and the engine compartment. There are also youtube vids and some how tos at dieselgiant.

The problems you've listed all fit into my learning by trial and reading while in school which was before the easy information access of the web.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.