2003 Chevrolet Cavalier thermostst replacement

If you follow the upper hose back to the engine that will lead you to the thermostat housing, should have 2 or 3 bolts that hold it on. So drain some coolant out of the radiator and then remove housing, replace the thermostat put the cover back on and replace the coolant. Start bring to full operating temp and then let cool remove radiator cap and check coolant level, top off it needed and that's it.