How do you replace the thermostat located on a 1992 Chevy Caprice Classic?

Drain radiator; drain at rad petcock or just remove one end of lower hose; you don't have to drain it completely just enough so coolant is halfway down. At the lower end of the large top black hose is the water outlet which is attached to the engine with 2 bolts, remove them . Water outlet may need a little prying but do it carefully. Thermostat now can be removed with your fingers but note how it sits in small groove and its direction. Clean all old gasket material off of surfaces. Install new stat making sure it sits properly in the retaining groove. Use a gasket sealer on gasket; any will do. Now install the two bolts AND SNUG THEM EVENLY DO NOT OVER TIGHTEN OR YOU WILL BREAK THE HOUSING. Tighten all connections and fill with coolant. Leave the rad cap off and let it run for 20 minutes and vary the speed. This step bleeds air out of the system so the heater works and engine cools properly. Good luck.