It's definitely a scam.

"The way it works is like this: the buyer (usually claiming to be a broker representing a wealthy buyer or group of buyers from "whereever" (Sierre Leon, Israel, United Arab Emirates, South America or even London, England) sends a check for payment for the car. The check is for too much money, so he asks the owner of the car to cash the check and then send the overpayment back to the him. So the sting is that they get you to send the money back before you know if their check has cleared. Banks can't tell if the check is real for up to 17 days."

98 Contour V6 MTX, T-Red, 150k mi. Pic SVT Dual Exhaust, KKM Intake, Donnely Mirror, Dension DMP3 Player w/80GB of MP3s, Wheelskin 95 F-150 91 Mustang GT 06 Honda Shadow Aero