There is a vent hole in the back of the final drive gear case, so if you lay it down on the back side, oil will drain out through that hole. Do not spray water on it without first plugging that hole. I almost forgot that the first time I had mine off, and decided to spray it with degreaser and hose it off.
After you get everything back together, you need to change the fluid anyway.
The hardest part of removing the rear wheel is removing the right muffler, so you can pull the axle out. Easy to do, but usually ruins the very expensive graphite gasket. I always keep a extra one on hand, just in case.