Im undergoing this now, rear bushing & spring plate swap is quite an easy task - not much to mess up! Mine were bad, but not as bad as yours.

Pick up some rennline spring plates with bushings already installed, some new hardware and you’re golden. Lots of videos on YouTube of people doing this work to get your confidence level up. Search greasy finger Porsche, he has a ton of videos.

Yes! Big fan of his channel... His videos and a few others are why I'm thinking I could maybe take this on myself. The other question, though, is if I need also do the trailing arm bushings, which would be a total rear suspension teardown.

The original rubber in these cars is very durable. I didn't replace the the arm bushings on mine. They looked okay, and in order to do that job the first time you have to drop the transmission to get access to those bolts, so it's more of a PITA. I recommend that you first install new spring plates with the rubber bushings that are vulcanized on, see how that works, and save the arm bushings for a time when you have another reason to drop the engine/tranny, then do those if necessary.

On your 73, yes, but on later cars they are removable. not sure which year it changed, but on my 77 they are.

Presumably updated in '74 with the update to G body. I know on the '87-'89 its a little tougher to get to the bolts because the G50 trans housing is larger, but I'm pretty sure I've seen a Greasy Fingers video where he does it without dropping the engine/trans.

Lucky you! Me, not so much..

Nevertheless, I would still do the spring plates first, see how that works, before tackling the arm bushings.