If it were me, I'd cut my losses and get it as far away from that mechanic as possible. Get the engine put in the back of a pick-up and have the car towed to the guy your dad knows for evaluation since he knows a good bit about Porsches. Keep the message on your phone and have him sign a release for you to take the car and engine at no charge. You will never get him to put the engine back in since it took him 8-9 weeks to get this far when he was hoping for a job that would pay him back for the time.
I'm with everyone else as far as trying to sell it before having it fixed properly. Nobody will buy it for a decent price while thinking it may need a new engine. I'd put the Porsche rebuilt in that was suggested before and sell the one you have to a rebuilder (unless the $5K price includes swapping it for your engine) or keep the engine and rebuild it over time and have a spare.
Good luck!
