As mentioned you will want some rock sliders, and if you are concerned about damaging the bed and front fenders, good strong front and rear bumpers would be helpful. If you are looking to make it easier for you and your rig, a set of dual transfer cases are about the best mod you could do for the trails. Even w/o the dual cases you should be able to make it through, though how much damage you do to your rig will depend on your driving skills, and your ability to pick the best line through the trail for your rig.
Spare parts:
front and rear drivelines
steering components
hub
same size spare tire, and tire plugs
duct tape(to make tire plugs when you run out of the kit, roll up the tape sticky side out and stuff in the sliced sidewall
ratchet tie-down straps
heavy duty zip ties
set of long battery cables
spare pieces of steel and welding rods(the longer batter cable will be helpful)
tools to do all the repairs you might encounter on the trail
a spare coil and some extra spark plug wires are helpful but not nec. needed.