Honestly, while you are in there, replacing brake pads and wheel cylinder, do your spring kits as well. more then likely, its pretty rusted, and you should do it while you are in there. Also, they are pretty cheap, and not any extra work, since you will be taking the drum breaks apart anyway.
Wheel cylinder would be my guess. does your breaks have any pressure still? and if so, go under there and look at that tire, and have someone hit the breaks.
I hate working on drums, but have done it enough where it is not to bad. If you are fairly new to drum brakes, I would lift the rear end up, remove both tires, and work on one while keeping the other all together so you can look at the springs... I know someone (me) who thought it was a good idea to take both apart at the same time the first time I did it. A lot easier keeping one together to see where everything goes. Good luck, and I wouldn't drive it til you get her done. Good luck.
