To replace a thermostat in a Volkswagen Corrado, start by locating the thermostat housing, which is usually connected to the engine block or cylinder head. Drain the coolant to a level below the thermostat housing, then remove any components obstructing access to the housing. Disconnect the hoses or pipes attached to the housing and remove the bolts securing it. Carefully remove the old thermostat and gasket, clean the mating surfaces, and install the new thermostat and gasket. Reassemble the components, refill the coolant, and verify proper operation of the cooling system.