[cary]

I don't know where he'd use an impact wrench ? Maybe I missed something. ??

One thing to remember, the T-stat is just hanging there, between front and back lines. I use BIG ASS slip joint pliers to hold it in place. As to not twist the lines.

Go slow. Give it a little twist tighter to try and break the corrostion. Then slowly back them off. If the PB Blaster did it's magic, it will go easy.

If it goes my usual way. Get out the Dremel. Put on the cutting wheel. Carefully split the nut.
Easy deal. Keep an eye on the filings. You don't want them back in your oil.

Good Luck