How do you replace the thermostat on the 2004 gmc Denali?

To replace the thermostat on a 2004 GMC Denali, first ensure the engine is cool and disconnect the negative battery cable. Drain the coolant from the radiator, then remove the upper radiator hose connected to the thermostat housing. Unbolt the thermostat housing, take out the old thermostat, and replace it with a new one, ensuring the gasket is in place. Reassemble by reversing the steps, refill the coolant, and check for leaks.