How do you change the thermostat on a 2000 VW Passat?

Should be located in a removable housing at the engine end of the upper radiator hose Drain about 1 gallon of coolant from radiator
Remove this housing
Make note how thermostat is installed in housing
Clean both surfaces
Replace thermostat and gasket
Re-fill coolant system slowly to prevent an airlock
Start engine and check for leaks
Run engine to normal operating temperature with heater on
Re-check coolant level