over heating

When the car's fully warmed up, feel at the bottom area of the radiator to see if it's as hot as the top part. After sitting for 2 years, it's possible that the radiator's plugged and it would be the bottom area where the gunk accumulates. I use a remote thermometer (reads infrared light indicating temperature) to check for plugged radiators. A radiator shop or a good mechanic should have one of these tools. Here's a directory link for you: http://repairpal.com/chevrolet-repair-in-lame-deer-montana

You probably have a air pocket in the cooling system. I had the same problem with my Cavalier. All you have to do is take off the radiator cap, then open up the bleeder valve on the pipe that runs from the firewall and around the motor (on the right side of the motor if you're looking at it from the front) and put a little bit of coolant in the reservoir, wait a little bit and coolant should flow out. When that happens, close the bleeder, and your problem should be fixed.