Recently my 4cyl 98 tj is having problems going into first and reverse. Bad to the point where I'm straining to get it in. I replaced the clutch about a year ago and put in a centerforce dual friction. It has been fine till recently
First check and see if the hydraulic clutch reservoir needs dot3 brake fluid it's located on the fire wall on the driver side it's little black cup with a black lid!! Most likely that's probably low making it hard to engage the gears.
I'm not sure on a jeep because I haven't had to buy one yet but on my old chevy race truck I believe if I can remember was about $80 but that was along time ago that I had to replace it, try about 14yrs hahaha!!