Deal sounds good. Just make sure you talk to him face to face on a large transaction like that, eh?
Make sure it is not a internet fraud before committing any hard earned money.
If you do end up getting it, congratulations!
P.S. Questions to ask:
1. Why does BMW not have license plates?
2. Mercedes being sold by same seller has Texas plates yet says M3 is in NJ/Philadelphia?!?
If I was buying $20k+ car, I would go to the seller personally and pick-it up myself instead of relying on electronic transactions.