the best way to do it is to lift the rear of the car off the ground, the front is ok to stay on the deck.
remove the rear wheels.
undo the driveshaft bolts and lay end gently on the ground - 15mm and 17mm i think.
take the breather hose off the diff (passenger side in the same place as the brake lines)
undo the brake line that comes off the body and goes to the diff, at the diff end. plug or compress the rubber hose slightly to stop all your brake fluid dripping out, if the master cylinder goes dry you will have a lot of problems bleeding it properly. 10mm each side, and keep the copper washers.
undo the handbrake cables and get them out of the way. (remove the retaining clip and twist the hook out)
undo the watts link at each end where it attaches to the body. 19mm and 18mm i think, or just a 19mm each side, some are different to others
undo the swaybar bolts at the diff (13mm, and either a bolt and a nut each side or just a bolt)
undo the upper and lower control arms where they attach to the diff. 18mm and 19mm, or may be same as above
support the diff with a trolley jack under the center, and undo the shock absorber bolts at the bottom (not the ones inside the car) 19 or 18 and 19mm...
get a mate to hold one end of the diff to help guide it out, and slowly lower the diff at the same time as you pull it backwards out of the car, removing the springs when its possible so they dont fall out and bounce around.
then when its on the ground away from the car you can easily swap the brake callipers and rotors over.
then put it in the same way - line it all up and put the springs in their seats, put in the shock bolts first and let the diff hang from them while you do all the other stuff, make sure the springs are seated properly at top and bottom as you are jacking the diff up into place.