The third member weighs a little more than 25 pounds, and an axle housing is light as a feather. It's the drums and shafts that are heavy, but you'll pull those and move everything in pieces.
Put the rear frame on tall jackstands, chock the front wheels WELL. Jack up the rear axle, remove the wheels, put it on stands too or let it droop for now. Remove the brake lines, soft line between the axle and body and hard lines at each drum. Unlink the ebrake cable. Disconnect the ABS sensors, if it has them. Four bolts on each axle flange hold the shafts in, unbolt those and slide the shaft/drum assemblies out (don't let them rest on the axle seals, remove them completely). Now you can unbolt and remove the third (and depending on how much the yard wants for it you may as well buy it and sell it, since you put in the labor to remove it). Unbolt the sway bar, take the shocks off, and droop the axle so that the springs fall out. All that's left now is the axle housing - support it so it doesn't twist and fall, and unbolt the four links and you're done. Barring complications, figure on two hours.
