Well, ended up changing the oil with GN4 10w30 and the front/rear diffs with Royal Purple 75/140. Oil came out very clean, as expected, and I honestly can't imagine paying a dealer to do it (I would like to know how to check the valves myself though). I don't think I'm going to cut the access hole for future oil changes...it really didn't take very long to remove the pins/screws/panel/electrical plugs. Pretty sure next time it'll be about 15-20 mins from start to finish.