Josh,
Like Truckernix said - the shop manual is pretty descriptive.
Master cylinder comes apart fairly easy in a vise. Once its opened and you've removed the plunger etc, you can inspect the cylinder walls for pitting. Pitting is bad - There are options for honing / sleeve - or you could just replace the whole thing for just over $100. A rebuild kit is available from most vendors for cheap.
ALL my brakes were seized when I got my truck, and the neighbors got to hear some choice language as I removed the drums! I ended up buying all new wheel cylinders.
Finally - yes, you won't find rear 1-ton drums very easily. My guy machined them lightly to try and preserve them. If you can find some in a yard - grab em.
My brake work here...
http://1949chevy.com/index.php/brakes/Good luck
