How do you change a thermostat on Renault Laguna 2.2 Turbo Diesel?

To change the thermostat on a Renault Laguna 2.2 Turbo Diesel, first ensure the engine is cool and disconnect the battery. Remove the coolant hoses connected to the thermostat housing, then unbolt the housing and take out the old thermostat. Clean the mating surfaces, install the new thermostat with the correct orientation, reassemble the housing and hoses, and refill the cooling system with the appropriate coolant. Finally, reconnect the battery and check for leaks after starting the engine.