Yep, I've seen this type of scam before.
The check is worthless, Since it looks like a cashers check your bank will take it and give you the cash, by the time your bank gets to transfering the funds from the bank the cashers check was drawn against that account if it was ever real is closed, which leaves you hanging. Since by that time you have already sent back to this guy the $5,500 which he gets "real" money. then your bank comes back to you for the full $13,000
I would send a reply back and let them know you are not interested in selling your vehicle to them.