How do you change a thermostat on a 2005 Chevrolet Avalanche?

To change the thermostat on a 2005 Chevrolet Avalanche, first, ensure the engine is cool and disconnect the negative battery cable. Drain the coolant from the radiator, then remove the upper radiator hose and the thermostat housing, which is typically held by bolts. Replace the old thermostat with a new one, ensuring the gasket is in place, reassemble the housing and hose, refill the coolant, and finally reconnect the battery. Start the engine and check for any leaks.