the motor should be fine with those miles....but i couldnt say that much for the tranny or t-case. could go forever or could not.
if its leaking WATER, its not the water pump...the only thing that water comes from is the A/C....correct me if i am retarded and completely wrong anybody. but i in my experience have never seen water come from a water pump unless they are putting straight water in the radiator...
but either way, yes putting in a new water pump on a 4.0 is a very easy fix. and the WP only cost about 40 bucks.
and no, your f150 hitch wont fit, your f150 has a frame, the ZJ has a unibody.