My 2 cents-
Either get a PPI done by an independent Porsche mechanic/specialist $100-200+/-.
Or...get a decent warranty from the dealership.
I bought my 99 Porsche with high miles sight-unseen (ebay) it was dirt cheap.., no PPI and later took it to an Indie specialist after the fact. Passed with mostly flying colors so I was fortunate.
Take my advice though and don't take a chance!
Drive it, shift it, listen to it, look at it as best you can...and you'll know if it's good or not!