[Landseer]

If you have experience with mercedes or bmw, some will transfer, but you still need wiring diagrams and other documentation specific to the 928 and will need study it enough to know how the buckets of information are organized. That documentation can be owned for $70 or so.

Car knowledge in the form Japanese or Detroit car experience doesn't help much on these.

About twice a month on these boards, like clockwork, some mopar or ford or camaro guy shows up with a puffed out chest and a cheap 928. They get spanked by the car, really their lack of study habits, and get angry because the car is worth less than they thought.

In fact, one major issue with these cars from inception was the inability / unwillingness of the dealer personnel to learn them. Very complicated. Money loosers for any tech who touched one.
Few others ever invested the time.

Now, 20 to 30 years later, lots of rummage sale buyers show-up demanding answers to technical questions. That pattern shows up pretty quickly, so there can be frustration with their lazy approach, especially when the motivation is from a used car dealer type looking for info to patch a 928 together just enough for a flip.

That's also why so many ailing ones are sitting. Normal car guys don't take the time to figure them out, yet they look so complete and solid as they sit in suspended animation that owners cling to them. Lately, as the owners aged and the economy has turned, there has been a kind of spirit of riddance that has put many into the market.

Best advice is learn to fish, ie, read the tech manuals on these if you want a good ownership experience.