Uhhh... If this is the same "full floater" axle as my 58 1 ton (more or less the same, and I think it should be) then pulling the axle shaft is easy. Undo the 8 bolts holding the axle shaft flange to the hub and pull the axle out. There was originally a metal gasket between the axle shaft flange and the hub. People regularly don't save these. I've heard they can be purchased. Same as the "GM 14-bolt" axle shaft flange to hub gasket (a VERY common axle). I just cut some paper ones out from some gasket material I had. They work fine.
What's going to be more of a problem is pulling the hub / drum piece (they are connected with the wheel studs) off of the axle. Just remove your grease cup and take off the big nut / washer / nut holding the hub onto the axle. Hope your bearings are in good shape!?. Now how tightly adjusted are your brakes. If they are loose, then you can pull the hub / drum off easy and get to the brake guts. If they are tight then you can't pull the drum off yet. You have to remove your little brake blocker thingy (don't know the name of it) from the bottom of the back of that metal plate that holds all the brake guts. Then you have to back off that little thumb screw looking thingy (don't know the name of it either) so your brakes are far away from the drum.
Now everything should come apart and you can replace your wheel cylinder. A picture is worth a thousand words, and the words I've typed won't replace having a manual lying around.
My rear bearings were in great shape, so I did not need to replace. I had plenty of brake pad left, so didn't need to replace. My cylinders where shot and rusted out.
Pulling the brake drum off the hub is a bit more involved and requires a shop press and some new wheel studs. Unless your studs are in bad shape, I would NOT recommend doing this.
