Generally, that's what I'd have done, but if you spend $13,000 on an engine-job, and then the head comes loose, I think it's best for the dealer to "deal with it".
Thanks for all your comments guys!
Just an update:
The seal they put in blew after 2 hours again. Found out they had stuck silicone on the head gasket (yes, I was there when it was being put on, but the gasket was already on the block, and seems the guy put the silicone between it and the block). So, the tractor went in, again... They took the head off, but this time I wanted to see the d**n thing. Guess what? The fire-ring had worn a slight groove into the head, and at the point were the first gasket blew, you could see/feel erosion marks. I told the (get this!) service manager, and he kept saying, "oh no, it'll be fine - they are too small, no problem, no problem, I'll guarantee it's going to work!" I drove it home, and by the time it rolled into the yard, it was leaking again...
Oh, and as for newer equipment, they actually ship the stuff with "computer bugs" (their words, not mine) to a different JD dealership 2 hrs away...
That's what you get for living in the parkland.