i don't know if your 98 is different from my 01 or not - but on the 01, you don't have to pull the dash or do anything overly complicated. your mechanic might be exaggerating.
you do need to remove the knee panel, and maybe? the column covers, and the dash trim bezel thingy.
under the dash is a small white plastic wheel that adjusts the tension on the cable. the cable is small, not more than 1/16 inch or so. mine was a plastic, maybe green in color.
one end of the cable is attached to the shifter lever, so if you move the shifter back and forth from one extreme to another, you might see the cable moving.
the PRNDL indicator is a bolt in module in the cluster. its spring loaded to one end or the other? and the shifter moves the red line indicator back and forth. with the cable broken or disconnected, the indicator goes to the spring end, probably disappearing from sight.
if the cable is broken, you'll need to remove the cluster. its just unplugs by pulling it straight out (with prndl cable disconnected), and sort of wiggle it out. flip it over and replace the PRNDL module in the back side with a new one, or at least a new cable. i don't know if the cable itself is replaceable or not. i replaced my cluster once, and had to move my PRNDL, because the junkyard had cut the old cable.