Search the internet scam sights (Snopes, etc.). This is a common scam out there. I chased the luer on a scam just like this with a Z8 2+ years ago. Exact same type of reply from seller, etc. etc.
I told the seller I would coordinate the enclosed pick up of the car and transport (both ways) with a local reputable company (with approval of owner) to a BMW dealer for PPI, all expenses paid. If it passes PPI I would fly out and inspect the car with a cashier's check in hand.....never got a reply back (this after he was returning e-mail vollies within 20 minutes).
I have a real G4 ACR you can touch and feel for sale in the classifieds or a lightly modified G1 RT that may interest you.