How do you remove the thermostat from a 2001 Pontiac Montana?

To remove the thermostat from a 2001 Pontiac Montana, first, ensure the engine is cool and disconnect the negative battery terminal. Then, drain the coolant from the radiator and remove the upper radiator hose connected to the thermostat housing. Unbolt the thermostat housing, remove the old thermostat, and clean the mating surfaces before installing the new thermostat. Finally, reassemble everything, refill the coolant, and reconnect the battery.