George,
first, get your parts before starting, it sucks to have the car on stands waiting for parts. new cylinder at a min.
ok, so, jack up the car, remove the wheel, secure the car.
look on the back of the dust shield / backing plate and you should see 2 large nuts one on each side. if you have these they are used to set the brake shoe adjustment. turn one or both i think counter clock wise and the drum should loosen. loosen both and the drum should spin freely, you may need some soft taps on the brake drum with a piece of woood and the drum will come off.
If you do not have these your rear brakes have a spin wheel inside the drum, your owners manual should have a section on the brake drums.
now, once you have the drum offf you wil see the cylinder, I just bought some new ones they were not expensive. Pay attention, there are 2 pins that insert into the cylinder, these connect the cylinder to the shoes. one end is slotted, keep these, you can get new ones from K&K. they are about $12 each, you should be able to re use your old ones.
be careful when removing the metal brake line from the cylinder so you do not bend it.
Also, be careful not to get brake fluid everywhere, it will remove the paint.
R/R the cylinder, pins, re connect everything, bleed they lines and you should be good to go.
It may be a good time to R/R the rubber connecting brake hose from the splitter as these do get old.
good luck,
matt