I have a bad freeze plug and would like to know how to replace it.

I had same problem. Not enough space to get at it. I replaced mine (after it just blew out) bought one of those rubber and metal plugs you stick it in the hole and tighten the nut/bolt up it expands til tight. expandable freeze plug I think its called got it at Auto Zone. Hopefully they'll sell you the correct size one for it,sure dont want one too small or it will never seal up. Hope this helps. And when you are filling it with coolant always park it so that the rear of Jeep is lots lower than front,so coolant will reach rear of head or heads and have it running so it will burp the air towards the hihest point of eng. The 4.0 is bad for having hot spots in head due to having air pockets in the head where coolant should be thats why my rear freeze plug blew out. Jeeps are a beast of thier own nature!!!!!