Ah, I see what's going on now. The replacement regulator comes as the whole thing, not just the piece that receives the cables and slides up an down. The other reason you can not replace the slide by itself is that on the updated regulator, the cables are encapsulated in a small metal box.
You will have to remove the whole assembly. Which means:
1) unscrew and pull out the motor and leave it wired to the door, set it aside.
2) use a 4.8mm drill bit to drill out the five rivets, carefull, use only light pressure and high speed and let the bit do the work. If you press hard, the bit will catch the rivet and the rivet will just spin in it hole.
3) you have removed enough of the foam/vinyl barrier so that the assembly can be worked out from the door.
replacement is in the opposite order, and you already know how the window itself must be forced on to the slider.
You know, with as much head ache and perhaps four letter words going into work on the early 140's...it's fun isn't it? I bought the car used, a 93 with 100K. and in 6 months I have replaced the RR window regulator, instrument cluster bulbs, headlight wiper motors, other small things. The closing pump has problems, and the interior rearview mirror is loose. I hope all major updates have been done before....
think of it as slowly making your car newer with new parts.