Drain a enough of your antifreeze from your engine so that it doesn't come all the way to the top of the radiator, about 2-3 gallons ithink. Then, follow the top radiator hose to the engine, and where it connects is a little neck thing. Pull the hose (you might spill some antifreeze), and then pull the two bolts holding down the neck, and pull the neck off. In there is the thermostat, install the new one just like the old one was and put it al l back together. You might need a gasket, i'm not sure what the vortec engines use.