I just did this last weekend, and thought I would share some pics and my experience.
Please note that this is ONLY for the Jeep Wrangler TJ models with the NV3550 manual transmission. While other transmissions are similar, there may be small differences, including the location of plugs, types of fluids used, and other necessary items. Always check your particular vehicle to be sure before beginning.
To begin, you will need the following:
3 Quarts of Synchromesh or similar gear oil, a pumping device or funnel.
A 17mm hex bit, a socket wrench and possibly a breaker bar.
Not shown is an oil drain pan and some anti-seize lubricant.
Step 1 - Get the vehicle up on jack or ramp stands.
Step 2 - Ensure you can loosen the FILL Plug, located on the driver's side of the housing, BEFORE opening the drain plug.
Step 3 - Open the drain plug and allow the old gear oil to drain out.
Step 4 - As the fluid drains, inspect the drain plug. As you can see, it houses a magnet to catch stray metal strands. This should be cleaned before reinsertion.
Step 5 - Apply a small amount of anti-seize compound to the drain and fill plug threads. Then after reinstalling the drain plug, use the pumping device or funnel to deliver new clean fluid to the housing. Fill to the bottom of the fill plug, approximately 2 liters.
Step 6 - Reinstall the fill plug, then take a short drive being careful to observe shifting smoothness and then check for leaks.
Step 7 - Dispose of the old fluid in a responsible manner. Do not just dump it in the sewer grate down the street because you figure if BP can do it so can you. That is not responsible. Just take it back to the place you got the tools and fluids from, they will likely be able to recycle it for you.