Check on Bay 13 Volvospeed. Good instruction on drain points. One is under the backside of the engine and one under the radiator, driver side. Both are 13 mm. When I do mine I usually also take off the bottom radiator hose so I can backflush with a garden hose. When the water is clear, button it up and use a 50/50 mix. Really is easy, but check Bay 13. They have instructions on how to change the ECT and thermostat included in that section.

When refilling you will notice that coolant level will drop a few times, so just keep an eye on it and fill to the mark on the resevoir.

dick