It is a simple change out, unless going to the other type motor. The mount for 16 valve and 8 valve is different, but nothing a torch and welder can't fix (I would recommend getting the right one). The steering shafts are different length, so get one with the steering box. They bolt up same place as manual steering. Your bolts may be stretched from larger tires and rocks & things. (My front bolt was a bugger removing and a pain putting the new one in its place.) Same belts work.
I never really noticed a change in mileage, but steering is much easier, especially on the trails.
You probably DO NOT need to adjust the steering box. If you do read about it, the adjustment is made at full turn. If adjusted at midway it puts lots of pressure on the box at full turns.
I did not have the wiring for the pressure switch on the pump, so it isn't hooked up (not required). There is a write up to add an extra washer under the spring in the pump to increase the pressure, if normal power steering isn't enough.
I didn't think I needed it until I had it in. Nice addition.