Yeh me lol, very common problem on Fords, the bolts holding the t-stat case to the intake manifold seem to seize a lot. Mine snapped, it was seized bad. Took 4 hours of heat and slow drilling to remove at friends shop, including a couple days of penetrating oil sitting. If you attempt it yourself, you'll have to try a combo of ratchets and extensions, as the casing is in such a tight area there isn't a lot of room, my smaller ratchets would fit in but not strong enough for how bad the bolts were seized, my thick craftsman with an extension worked....and snapped the bolt in the process.
Replacing the t-stat is easy though, once the case is opened, just pop it in, but make sure in the same position as the factory one (some will put it in reverse etc). I used a Motorad Fail Safe and drilled two small bleeder holes in it.