How do you replace the thermostat on a 2000 GMC Jimmy?

To replace the thermostat on a 2000 GMC Jimmy, first ensure the engine is cool and then disconnect the negative battery cable. Drain the coolant by removing the radiator drain plug and then remove the upper radiator hose from the thermostat housing. Unbolt the thermostat housing, take out the old thermostat, and clean the mating surfaces. Install the new thermostat, reassemble the housing and hose, refill the coolant, and reconnect the battery.