It smells like a scam, don't put much faith in him if he does respond back with an MOS and unit, if it is a scammer he's savvy enough to use google to get the information he needs to answer any military question you may have. In most cases scammers will say they can't pick the car up themselves but will arrange for it to be picked up, if you agree to sell it to him, tell him to have his people meet you in the parking lot of your local police department to pick the car up. Don't agree to a night time pick up or meeting place of their choice, I also wouldn't invite anyone I had any suspicions of to my home to pick the car up. If they refuse to meet you at you at your local police department it's a scam. As someone else pointed out, it could also be someone just trying to get as much of your private information as possible by leading you on that they're going to buy your car, they then sell that information or use it to try and access your accounts. Questions he'll ask "So I can pay you what's your PayPal information, so I can pick up the car what's your address, what's your telephone#, what's your email address, etc, etc."
Then again it could be just a deployed GI that really, really wants your car, but as a litigation and fraud consultant; I would say it's more likely a scam than being a legit offer. Proceed with caution my friend!