Get to the library and look in Chiltons or some other good auto repair manual, so you understand where everything is and how to handle it. Buy a thermostat and gasket. Drain your radiator. Open the thermostat housing and take out the old thermostat, watching which way the spring side goes so you can put the new one in the same way. Put on the new gasket and close up the thermostat housing and refill the coolant. Before you do this, look at your water pump carefully and feel around it. You want to know if it is leaking. There will be dampness behind the pulley and you will see a powdery, pinkish deposit in that area where coolant has dripped out and dried. If it leaks at all, replace it. That might be your whole problem. The job is easy.
Do not let that all aluminum engine overheat. Turn on your heater high to bleed off extra heat until you can pull over in a safe place and refill the radiator while the engine is running. Be careful opening a hot radiator or you could get scalded.
