I'd suggest you replace the unit from a wrecked combine. It sounds like a bearing went, chewing up the gears and taking out the seal. Even the bearings are expensive, and replacement gear prices are out of sight. Good luck.
I'd have to agree entirely. We munched one on the 750. Well, actually, pretty much locked up. Would move a little and lock up. After splitting the housing and looking in I was in no way going to fight trying to rebuild it. I will warn you. That is one heavy hunk of iron. After debolting it make sure you have your good loader chained to it so it doesn't hit the ground or more importantly your foot.