I don't know if it is similar to my 87SDL seat operators, but inside the thick black cable that runs from the electric motor to the seat frame there is a flexable shaft. The shaft is hardend steel and looks like a spring that has been compressed from its' original round shape to a square shape. The easiest way to work on this is to remove the entire seat and then flip it over gaining access to the motors. Four 10MM bolts hold the seat to the floor pan one at each corner, you may have to move the seat forwards or back to get access. Plastic trim covers have to be removed first. A 10 mm gearwrench with a 5 degree swing makes the rear bolts easier to get out. Once you've got the bolts out you've got to disconnect the electrical connectors at the front of the seat, you grab the carpeted trim piece and pull it forward to release it and lift it upward the connectors are underneath. Disconnect the battery to be safe if you don't want to short anyhing out! Pry up the connections.
Lift the seat out of the car and invert. You can undo the springs that hold the carpeted trim cover and remove it out of the way. You then need to loosen the bolts holding the motors to the frame on one side and (on my SDL) the memory box on the other side freeing up the motors.I had to unscrew the six philips head screws that hold the motors to the frame holding the cable housings, then I was able to pop of the C-clips retaining the black cable housings freeing them. You may be able to release the C-clip retaining the flexable cable housing without disassembling the motor frame if your lucky. If you can do that pull the cable housing free of the motor and you can grasp the flexable steel shaft and remove it. If its broken into multiple pieces you can try to get the piece out with a magnet or most likely you will have to go to the other end of the cable housing and using a pair of pliers compress and release the sping clip holding the cable housing to the geared frame mechanism, this is a strong clip. Pull the flexable shaft broken piece free or push it through and out.
I had gathered a couple of spare flexable shafts at the junk yard when I got a new seat spring frame. You may be able to buy them new from Fastlane or you can get them from a salvage operation I seem to remember seeing them somewhere for $18 or $20. You then replace these shafts and reassemble in reverse order.