No, you do not have a 'freebie' back into the Marine Corps. You would have to compete with everyone else for a spot.
As for what your chances would be... Well, I guess it all depends on how bad you want it, right? If you're willing to bust your ass in school and in Marine-related activities, and if you're willing to go to the Leatherneck program and dominate, then your chances are pretty good. If you're a turd, though... Those usually get flushed. Unless they're a Monkey Turd, then they get tossed...or eaten, monkey dependent.
All kidding aside, if you'd like some info, shot me a PM, and I'll do my best.