Major goped problems?

i rode my goped from work today and the motor just stopped for no reason, didnt bog down or nothing. now it wont start at all, cant pu the cord and the spindle wont budge, and theres black stuff all over the place that looks like burnt oil. it was sitting outside all day, but started up and ran fine and i never had any problems out of it before, what the hells goin on???? is the motor seized, if so is that a big problem? pease help