Bummer.
May sound like extra work, take fuel tank and carb off, stand it up on grab bar, add little heat to case around plug.
This is for safety/fire reasons, failure to do so leaves consequenses on you.
same thing happened to me.With a newly aquired blaster.
this is what i did.
warm the engine up if you can.
stand the quad on it's butt end straight up.
then the only thing that would take it off,
in my case was locking a pair of vise grips on it/sticking straight out,
then putting a pipe wrench on vise grips to turn it/while holding the vise grips
steady to not come off.
the shop told me to chizel it/but i tried with no luck
If you have a welder you can weld a large nut to the drain bolt from the inside of the nut, the heat from welding it would also help to free things up. Then you could get a socket on it.