The first poster needs to put it in simple English: To find the thermostat, first find the upper hose on the radiator. Follow that hose toward the engine until you find the elbow piece where the hose meets the engine. If you remove that elbow piece, you'll see the thermostat in the "hose line," or the thermostat will fall out.
To replace the thermostat, you'll need a new thermostat and gasket. You can get them at NAPA or AutoZone or any major auto parts store. Scrape the old gasket off the elbow piece and put the new one in place. The thermostat goes in the hole under the elbow piece, so once you bolt the elbow piece back in place the thermostat will be held in place. Make sure the new thermostat goes in the same way as the old thermostat -- many of them have markings to indicate which side goes toward the engine.
