Thanks to the details provided in
this post, I was able to change my front and rear diff oil today. I used
Redline 75W-90; two quarts did the trick (about 1.2 for the rear and most of the rest for the front). The pictures from
this site helped as well.
The toughest thing was getting the reinforcement off and back on. It has eight bolts; six of which have free spinning nuts on top (those bolts should be tightend to 56Nm). You have to put a wrench on top of them to hold the nuts from spinning while taking them off and putting them on. I used a box wrench and really had to work to find a way to get them in the right position.
I did not have to jack the car. In all, it was about and hour and a half (mostly spent on the reinforcement plate).