Car temp going red, then cooling down while highway driving.

Update, since it won't let me edit the question. I replaced the thermostat with the correct gasket today. Nothing leaked when car was on. I also pulled the hose of the coolant pipe under the car and fluid poured out, so that seemed ok. I then drove it to work, and it stayed at middle temp until I got almost there (about 10 minutes into the drive) and it pegged at the red line and wouldn't budge. I pulled over and parked it, shut it off. It started expelling steam from different points on the engine. Pretty sure the head gasket might be done for, since the oil light came on before I turned it off. I waited for it to cool off, then drove it to work, the oil light was on the entire way, but no white smoke came out of the exhaust. Maybe it's the water pump? I don't know.

Another update. Drove it home from work at about 50 mph all the way there. Drive was about 15 minutes. Car stayed at 100 until I neared the 13 minute mark an when I kicked on the heater. It then started slowly creeping up but never got above midway. I did smell oil burning, though. Interesting to note is that my heater never actually blew hot air. Only cool air. I think the heater core is located in line after the waterpump, since GM likes to use the ambient heat from the coolant to speed up the heating process. This further leads me to believe it's the waterpump. On a 2.4L engine, the water pump is tied in with the engine's timing system, and is located on the backside of the engine. The local shop i go to quoted 6 hours worth of labor to change. I really hope it's not the pump, but it's either that or the head gasket. Engine had zero coolant the, no steam coming from it when it heated up on the way home, so it may not be the gasket.