Awesome, thanks for the reply Gearhead. We'd already ordered the thermostat / housing assembly, I just wasnt sure if I needed to continue looking for cause of AC problem. By the way, part was $143 @ Autozone or $33 @ RockAuto.com. Same AC Delco part!
I did notice there's a blue paper type gasket on it currently. The AC Delco housing we ordered shows an O-ring in the picture. I'm assuming no paper gasket is needed with that. Correct?