Glad you got through it. I've helped JSeabert next door through this twice on his 93SSE. That gasket kit? $168 thru gmpartsdirect. It includes head gaskets, lower intake gaskets, upper intake seals, valve cover seals, and Thermostat housing gasket That won't do you any good if you're in a hurry, though. What the kit doesn't include is new o-rings for the injectors, TB seal, and something else....can't remember. Josh? Help me out here.
As far as the thermostat goes, he gave you the 'by the book' answer that GM wants you to hear. 2 of the mechanics at my local Pontiac dealer said that GM'* stand on the issue is that they can do no wrong, and they both said these drivetrains can benefit from the 180. Both are running it. One in a GTP, the other in a GP SE.
The point is to prevent this from happening again. The best prevention is to decrease the overall operating temps. That'* why the extra tranny cooler is also so highly recommended.
3 hours is pretty good. Not bad at all.
Glad to have you back on the road!