How do you change the thermostat in a 2002 gmc savana cargo van 1500 series?

To change the thermostat in a 2002 GMC Savana Cargo Van 1500 series, 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, replace the old thermostat with a new one (ensuring the gasket is properly aligned), and reassemble by reversing the disassembly steps. Finally, refill the coolant and reconnect the battery.