It is more likely to be a rear wheel bearing going out. . Not a simple fix on these .
I think the chain of events goes like this (and this is typical for Toyota trucks, it seems);
1) diff breather isn't long enough and gets clogged and stops being a vent
2) pressure builds up and blows out an axle seal, leaking gear lube all over the bearing (and brakes)
3) the leaking gear lube washes of the grease in the wheel bearing. Since the bearing isn't sealed from the axle housing side (the axle seal and the o-ring are supposed to do that)
4) since the bearing is supposed to run on grease, and not oil, the bearing goes bad over time
So you need to go in and replace the seal, the bearing, and all the brake pads (parking and disc).
I concur that the rear wheel bearing remove/replacement is not simple. But once #1 above happens, this is the result... (IMHO)
FWIW, the breather on my FJ60 got clogged and blew the seals out. Since the wheel bearings are in the axle and run on gear oil, they weren't trashed. But the seals were letting water in during water crossings...