you have to take the plastic piece around the shifter out to get under the shifter in the cabin, and remove the couple big bolts to lift up and remove the shifter assembly, and remove the cables from there, keep any little clips, bushings n things, dont loose em.
and remove the shifter cables off of the transmission keeping any little clips etc....
the 2 cables will be attached to the shift linkage, to the right of the engine looking straight down on top of the transmission..
and have fun gettin it through the firewall.
(probably easier to remove the tranny side first, then maybe you can pull the whole shifter assembly with cables attached out once the shifter assembly is unbloted from frame.)
If I remember right, that's all there is to it man.
Here's some pics I found on the net...
http://media.photobucket.com/image/st18 ... 3439-1.jpg
http://img481.imageshack.us/img481/2925 ... rgesl0.jpg
just remove both ends and get it out n replace it, but why you need to replace the cables, what's up with them?
-EDIT-
While you're doin that, I would inspect the shift linkage parts on the transmission for play or if anything is bent.. that stuff is easy to find and replace and gives the car a much better feel if those parts are old and crusty / loose.
and don't reuse any dried cracked destroyed rubber bushing parts, easy to get new, and really makes the car feel better.. I remember doing this on my Alltrac years ago.. found at a JDM engine shop all those little parts in perfect condition..