Rear diff oil change on 2013 forester xt 2 litre

If that sensor is near the bottom of the differential, unscrew it and use it as a drain. If it is further up, put a suction hose in there to draw out the oil. There must also be a fill plug that you can suction and fill through. I never liked taking the cover off the diff just to drain it. I certainly wouldn't drop the engine's oil pan to do an oil change.