I didn't know about that thermostat issue either, I have an '01 Impala that I'm pretty sure has a thermostat stuck open. My car never has hot air and the temp guage raises and lowers crazily, I know, it's not a good situation.
I'm glad someone realized that car doesn't have a 3800 in it, I was about to laugh at you guys for thinking a Cavalier/Sunfire came with such a big engine in that body style. I was thinking the 2.2 or 2.4 myself, shouldn't he be able to find a good engine or some parts from a junk yard, at least until he can get his mom's car running fine.