You'll need:
(2) quarts Gear Lube GL5
(1) 10mm hex socket
(2) crush washers

Keep the car on a flat level surface...slide under the car from the back and you should see this (bottom left silver bolt is the drain bolt and the top right one is the fill bolt):


Picture of differential from the rear:

Mines were on real tight so I had to use a breaker bar along with the 10mm hex socket to help break it loose...if you don't have a breaker bar you could just do this with an ordinary rachet...use your foot and "push" the wrench to help break the bolt loose.

Loosen and remove the fill bolt first, then get a container to catch the old fluid and proceed with removing the drain bolt. Once both bolts are out, wipe them off. The drain bolt has a magnet attached to it and as you can see in the picture below, all that black stuff on the paper towel were actually metal shards.

Replace the 2 washers, then tighten the drain bolt. Add the gear lube through the fill hole until it starts to drip out of the fill hole...I attached a little section of 1/2" plastic tubing to the bottle to help me get the new fluid in. Once the lube starts to drip out of the hole (approx 1.4 quarts) then screw the fill bolt back in there. Clean up the area and check for leaks.

If you have any questions, please don't hesitate to email me.

Where can i pick up the crush washers? and what size should they be?

Kind of the same question. I have changed it before but never the washer. I hate driving all the way to Toyota to buy a couple washers.

Oh yeah,, 75w-90 is what you use in the 400's?