To change the thermostat on an S70 takes about 1 hour. The cooling system is drained (this presents a good opportunity to flush the cooling system and refill with fresh antifreeze). The thermostat housing is removed, (it is secured with two TORX screw fasteners). With the thermostat housing removed you can see the Engine Coolant Temperature switch, (it has a small wiring harness with two wires and an electrical connection attached to it. The temperature switch and thermostat housing are located at the front of the engine near the power steering pump resivior. Ensure the coolant is cold when you drain it so you don not get burned and run the engine with the heater turned to maximum hot after doing repairs. Allow the engine to idle until the electric fans cycle on and off and top up the cooling system as required. Most shops will quote an hour or so to replace the thermostat and perhaps an other half hour to replace the ECT switch.