The Durango box is a pretty straight forward swap with some spacers. The biggest issue is really geometry on a lifted vehicle and the strength of the front frame rail (cracks). A hydro assist is preferable. It takes the load off of the frame rail and puts the power inline with the tie rod. This keeps the tierod from bending when you drop the drivers and stuff the passenger tire, while you try to turn. I can park my rig against a rock, then turn the wheel with one finger while the steering pushes the XJ away from the rock. It also is a dream to drive on the highway.
The biggest issue with a hydro assist is that you have to tear down the steering gear, then drill and tap, then clean everything before reassembly. If you have the tools and expertise, it isn't all that technically hard, but there are a lot of things you can do wrong just in the assembly, not to mention the issue of getting it adjusted correctly.
Also, if you are going to do your own, make sure you get the kit with the bearings. On the newer boxes, you simply can't buy a kit with the bearings, you have to buy an early kit and steal the bearings, then buy the newer kit for the seals. Also watch out for Edleman kits. While I have used them for over a hundred gear rebuilds, lately their seals seem to be crappy. I have had several leak right away, even when everything was done right.