Welcome to wild and wonderful life of owning a oddball KJ
What they may have replaced was the upper or lower control arms, they do wear out. Those are about the only things back there to replace.
NOW your lift idea.................not good and I will try to explain why. The Libertys have weak springs from the get go. They sag pretty bad after 50-80,000 miles. I've had them here with 75,000 miles and they would be sitting 1.5 inches lower than new.
So....if you were to combine those weak springs ( that are already sagged some ) along with any spacer type lift you may only get an inch of lift, plus a bad ride. Most everyone who does a spacer style lift ends up removing it for a full spring in a few short months.
Even if just driving to the mall daily a full spring lift will actually give you more lift, a better ride, better handling and will last 80-100,000 miles easy.
So really to do it right a full spring lift which has all new shocks and springs is the best way to go. I know being in college sucks with trying to juggle funds, but save up a little each month and you'll soon have enough $$$$ to do it right. Looks like a Rough Country is about 300 bucks, you're almost half way there . Look at the Ironman kit from jeepinbyal . Its a good kit, rides really well ( have tested it myself) and gives you about 2.25 inches of lift, which you can add a couple of cheap tricks to for even more
Enjoy your KJ