as everyone has said the release bearing or thrust bearing is on the top of the list, clutch and pressure plate swap while your at it. pressure plate could be worn as well
if the gearbox is off it is worth replacing everything in there for new due to the time cost and hassle of removing the box and refitting it. so its advisable to replace as a minimumthrust bearing (release bearing)clutchpressure platethere should be no reason to replace the flywheel unless it is scored to hell but then you wouldn't be able to select gears as the clutch assembly would be toast.the crank seal should then be easier to replace due to access, the seal in itself is a split assembly (if its the same as the 4ltr sorry cant remember) so there shouldn't be any issues installing
I gather your aware that the diesel jeep is only a part time 4wd system and for use where the surface is loose so as there is no slip system in the transfer/gearbox like on the 4ltr petrol
on a rare occasion that I had it in 4WDL....Situation:Reversing around 2 metres on wet grass after climbing (going forward) a steep, wet, grass hill for about 7 metres in 4WDL 1st.