I have a 79 4X4, the only thing i have had bad luck with is a wet dist. cap and wires on the trail. a bit of blue gasket sealer around the cap is helpful and some spray water displacer on the top of the cap and wires around the plugs is a good fix before hand. Out on the trail some paper towels or dry rags are great incase things do get wet. As for weak parts ,,,front hub bearings and seals need regreased and inspected they hate leaky seals,, and that will just kill the gears in your lock out hubs and bearings.
So you just got your truck, check front and rear diff's for clean gear lube and might as well do the trany while your under there. Look around for anything loose or worn. These little trucks are bad ass off road,

will take you places you don't really need to be. But thats the fun of it, isn't it.
Hope this helps a bit
PS: enjoy ...... I know i sure have >>>>>