This is a super straightforward process that I have no excuse for waiting as long as I did. 90k miles and it still has the original gear oil in it.
Do yours! It's cheap and easy. Here is what you need:
1.3 Quarts of 80-90W gear oil
An oil pan
A long funnel
21mm socket and socket wrench
Get the car up in the air somehow, I'm pretty sure I've told everyone here how to properly lift at this point, so there is no need to explain again.
Crawl under the car, behind the engine oil pan and in front of the transmission oil pan there is the differential. On mine its located right above one of the catalytic converters.
Grab the socket wrench, undo the 21mm bolt. It was a bit stubborn but not too bad. I always just spray PB blaster over everything anyway. Allow to drain, making sure to actually have the oil catch pan in the right place so you don't have to throw sand everywhere again. A piece of tin foil in the splash area works wonders here for keeping oil mess to a minimum.
Pop the hood, remove the air box and on top of the transmission on the passenger side is a dip stick. It's very hard to see and almost impossible to get a picture of. Here is a picture with the funnel going into where you should be looking.
Once the oil is drained, tighten the bolt back up and put in 1.3 quarts of your favorite gear oil. All done! Put everything back together and be happy knowing you finally got around to doing that.