Just tried to do mine (2011 SHO, non pp), here are a few things I thought of:
1. If you can remove the o2 sensor, you'd have a straight shot at the plug (I am going to try this next time)
2. You don't need to remove the wheel housing
3. Trying to get the plug put back in with the o2 sensor in the way is a pita
4. Trying to go from underneath was a no go, not enough room to wiggle my hand up in there, let alone the plug.
5. Keep your garage cracked and air flowing out, the oil likes to linger for quite a while...
I was only able to extract about 100 or so ml from mine, but when I filled it, it seemed to take an extra 100 ml, so like a few others that I have read I must have been low.
An idea that I am also going to try next time is to take some copper tubing that is bigger than the tubing I will use to suction up the oil, bend it straight and at the end bend it at somewhere between a 45 and 75 degree angle. Then from there, shove the tubing down the copper to where not only would it make it easier to get it in the plug hole, but it would help flex the tubing down into the transfer case. The other thing I wanted to try with this setup is to use some plastic hose/tubing that you would use to hook up a fridge or a filtered water tap. Not only is it small, if not smaller than the regular tubing people seem to be using, but it is also much more stiff to were it might be able to shoved into the transfer case more than a normal rubber/vinyl hose. The other nice thing about having the copper, is that when you are done, you can just pull the tubing into the copper and spare yourself from dripping oil on things like the heat shield like I happened to do. I'll make sure to post up some pictures when I do, maybe towards Christmas time when I have time off again and the fluid has been in there for a couple of months.
-Nick