FWIW, I don't think dealers do a good job of doing a PPI.
I think their sole objective is to find reasons to scare you away from buying the car so that you'll buy a used or new car from them.
On a car 10 years old or older, there may be things that are broken or on their last leg, like a/c, struts, etc., but if you think about it, every component on the car will have a different amount of wear. This is the subjective part. At what rate of wear on a particular item will the technician recommend replacement? 50%? 60%? 75%?
My car had been maintained at a particular MB dealer for the first 128,000 miles of its life. At 120,000 miles, I did the 120,000 mile maintenance service, and a whole list of items were recommended to replace, which I did, and the bill was about $1,200. At the 127,500 mile service, I got a different service advisor, and was given another list of over $3,000 worth of items to fix.
My instincts took over, I realized I was being taken advantage of, and I decided to find a good, local MB independent. I gave him the list, and he inspected the items on the car and only 2 or 3 items needed replacement in his opinion. Cost less than $400.
Sooooo, my advice is to find several MB independents in your area, talk to the owners or technicians, and chose one that you feel comfortable with.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".