Can someone point me to some info on how I should go about changing these myself? It's a 2002 montero sport

 

The rear differential is just a drain and fill.

Pull the drain bolt on the bottom of the pumpkin.
Pull the fill bolt. Allow all of the fluid to drain.
Replace washer (if desired) and return drain bolt.
Refill diff. until fluid starts to drain out of the fill hole.
I use Amsoil Gear Lube 80w-90, without any friction modifier.
(The LSD on my Gen III does not require any.) Although, Amsoil does make an LSD modifier. I'm not sure what lube you need for your sport, but if you check one of the on line manuals (or your owners manual) it should have the specs.

The brake fluid is drained out and refilled. Don't forget to bleed the lines and the HBB.
If you have a garden sprayer, I've heard of guys using it to exchange fluids, which then eliminates the need of bleeding, because it completes the process in a closed system.

Here is a link to the FSM I use for my full sized Montero:
http://www.pajero4x4.ru/piii/GR00006600-35A.pdf