If your plans include larger tires, then yes, upgrade to power steering. It's never a bad idea to replace the tie rod ends and drag link ends. One of the biggest improvements to steering is replacing the stock steering shaft that goes from the steering column to the gear box with a quality after market unit (I used Borgensen). A new steering stabilizer helps keep feedback to a minimum.
The preload adjustment on the top of the box can tighten it up. You use an allen wrench and another wrench to break the jamb nut loose and then you can tighten up the preload with the allen wrench. I've never done it, maybe someone who has can chime in.
There's no substitute for a physical inspection of the steering components, balljoints, and wheel bearings though. Any guess on your poll is simply a guess. Theres no need to throw random parts at a problem hoping they will make it go away, so inspect and determine what's bad first.
Rack and pinion IS a type of steering and generally not compatible with a solid axle vehicle. Google it if you really don't have an understanding of what rack and pinion is.
I have a friend who builds race cars and he is going to fab up the system when I figure out what I want. He made the recommendation of the rack and pinion because of the durability and that normally they come with 4 to 1 ration to help turn the wheels.
He knows my jeep and steering. I trust that much. He just did not know which system would be best for trailing.
Stock CJ power steering is 16:1 ratio, so quite a bit less effort than any 4:1 rack and pinion setup.
Thousands of vehicles have the same/similar Saginaw steering box found on a CJ. There's no question of its durability. Rack and pinion really isn't compatible with the type of suspension and axle arrangement on a CJ.