lol @ someone saying don't use a torch, its pretty common for a shop to.
PB blaster can be bought at autozone I think, this stuff works great!
If that doesn't work and you have snap on tools (or anything half decent) go with the hammering of a little smaller standard socket onto it. It is most defintly cross-threaded, maybe even rusted from the sounds of things.
Once you hammer the socket on, I'd suggest a breaker bar, maybe with a pipe on it too. MAKE SURE IT IS AT THE CORRECT ANGLE THOUGH. Hammer the socket on there good, and give it hell.
I see this all the time with lug nuts, some douche at jiffy lube cross threads the lug nut with an air gun. We ussually end up breaking the stud when taking the lug nut off thats how bad they are on there.