In the phone book
Depends what they check
My local shop spends 2+ hours with the car and for $300 that includes a leakdown test but they usually call before starting that to report what they've found so far since most of the time they can rule out cars before then.
Ask to see a previous report to get an idea about what they've found.
You can call any dealer and ask for an appointment for a PPI. They usually charge 1 hour labour.
Correct, dealers will do it.
IME, it was not one hour, it was closer to two. It's typically a flat-charge. Audi wanted $220 and basically ran it through their used car/CPO checklist and gave you a nice printout.
I actually used it as a negotiation point with the dealer: (A) you will deduct the cost from the price of the car, and (B) you will deduct the cost of any needed repairs from the price of the car. In the end that tactic netted me an additional $1k off the price I had already negotiated before getting the PPI.