Finally I got a capacitor leakage tester, err, Keithley 237 at a reasonable price.
Now I just need to find my stash of triax stuff and replace the FUBAR fan in the thing while taking a look for possibly bad caps. Aside from that, a quick poke at it suggests it's mechanically and electrically sound.
(Yes, I have many more plans for it, and I've always wanted an SMU, especially a high voltage one. The HP 4142B is huge and the high voltage card for it appears to be rare, so the 237 it is.)
Also, the shields inside the thing have like this fake leather vinyl on them!