I wouldn't be too hard on the dealer. For what it's worth a full diagnostic by a trained Porsche tech is not a bad value. Although I definitely did not pay $350. I think it was no more than $150. When my car hit ~60K miles (if memory serves) I brought it to the top dealer perhaps in the whole North East (Ray Catena Porsche, Aston Martin, Mercedes, Lexus, Jaguar, bla bla). I made the appointment to wait on site while the young tech went through the car top to bottom. Meanwhile I sat in what has to be the nicest lounge of any hotel or car dealer within 30 miles. Free lunch, internet kiosks, pool table, giant plasma on the wall. After a couple of hours the service manager dressed very professionally came out with a report that included the expected longevity of all the major gear, a true 50 point inspection. It even said which of my coil packs needed to be replaced. He of course did not try to sell me on doing a single repair because Jay Leno's or Dave Letterman's new McLaren SLR was sitting 20 feet away and they don't need my stinkin money.
I think the estimate was also about equal to the car's value at the time...which translates to about 30% of what my indy ended up charging for most of those repairs. But my indy is way too busy restoring old air-cooled cars (the ultimate recession proof business) to be doing these kinds of inspections. But at least I had a heads up on things my Indy would eventually be informing of later and played a role in deciding whether to keep the car or switch over to a newer car. I thanked the dealer receptionist lady for the free buffet lunch and went on my way. I think they even washed my car.