You've got his out of the press already?
If 'twere me....
All the hand wringing is good for a chuckle, init?
Anyways. Grab the die in a vise, some wood blocks for padding would be good, drill or saw access in to the interior of the case. Slow. No rush here. Use coolant. WD40, soapy water, whatever. lots of coolant. Go slow. Sparks and heat is bad, right.
Once you have a hole through the case, shake or wash out the powder. Water should kill the primer better than oil, from what I have read. But once the powder is out, you can pretty much set the primer off without too much grief. Earplugs is good. Eye protection too.
But I'd not bother. Trying to kill the primer, that is. Y'all ever seen reports of primers installed sideways, crushed flat? Yep. They can be. Not that it can be relied upon, but they usually need a pretty healthy whack to get them to go. If you want, you can just get it over with, and whack the primer with a center punch, while the hole in the now empty case is facing a safe direction. Gloves is good too!
Once the powder is wetted down or shook out, then it's time to start getting physical with the case. ViseGrips, channel locks, whatever. You need a grip on the case head, and want to go for rotary motion.
From there, I'll leave it to your imagination. Wear safety goggles and hearing protection at least up to the point that the primer is either cut off the case, or popped.
Worst case is that you lose the die. Pretty much where you were in the first place. Best case is no damage, and you know better for next time, eh.
G'Luck!
Tell us how it went.
Cheers
Trev