Just a little update...
Got under the truck at the weekend and, after some puffing and panting, managed to get the front driveshaft off.
Turns out the front (diff) joint wasn't too bad and the boot was intact with plenty of grease inside. The back (transfer case) joint, however, was drier than a dry thing on National Dry Day. The boot was perished, all the grease had long since left and the internal bearing housing had actually broken (which I assume was creating most of the noise).
Anyhoo, the new front bearing kit has arrived and I've now ordered a new one for the back, so once that all arrives I'll get it on and get off-road!
After that it's just brakes, front brake lines, front springs and shocks and clutch to do...!
Haven't figured out how to post pics yet, so once I do, I'll pop some up of my dry bearing.