The cable comes out through the front.

Open the sunroof part way, and unsnap the retaining clips that hold the inner cover to the sunroof (assuming yours is not a glass-panel sunroof).

Use a thin putty knife - slide it in between the cover and the roof - slide it side to side until you contact a clip and then gently rotate the knife to unsnap the clip. There are about 5 or 6 clips, if I remember.

Once the clips are undone, you can slide the cover forward and downward and remove it.

Close the sunroof and you'll see the attachment point for the cable at the rear of the sunroof frame. Two 10mm or 12mm-headed bolts, I think. Remove those.

Now go into the trunk and use the tool that comes in the toolkit to manually crank the cable out of the motor. There are instructions in the owner's manual for how to manually operate the sunroof when the motor fails.

The tool is a hollow metal tube with a hex-shaped end. You use a screwdriver through the holes in the end opposite the hex. There's a cover (or maybe just a hole) in the trunk lining through which you insert the tool.

FIRST - have someone in the car with a garbage bag or something to catch the cable. It has some seriously nasty moly grease on it and you do not want that stuff anywhere inside the car! It's not going to come shooting out, but you don't want to touch the cable or let it touch anything, if you can avoid it.

Turn clockwise to force the cable out of the motor. Once you've turned it enough to move the cable out of the motor gear, your helper can pull it free by hand.

Now - if the cable is broken, start by unbolting the motor from the trunk (remove the left-hand trunk lining to gain easy access to the motor. A bunch more 10mm or 12mm -headed bolts).

I'm pretty sure you can CAREFULLY detach the motor from the cable tube at the front of the motor, even with the cable still in the tube. The tube has a flange on the end that slides into a groove in the transmission.

Get the tube loose from the front (and probably from the rear as well) of the motor and pull the motor and included cable out of the trunk. Use the same method/tool to get the cable loose from the motor.

Once the motor and cable assembly are out of the car, you should be able to slide the sunroof manually. DO NOT FORCE it open or closed - you will break some of the mechanism trying.

Hopefully, the cable broke with the sunroof partially open. If not, PM me and I'll research how to get the roof open when it's shut with a broken cable - I'm pretty sure you can't just push it open.

Remove the cable from the sunroof in the same manner as before, except now you can just pull it free.

Once you go back in with the new cable, you'll experience the joys of adjusting a W140 sunroof motor to get proper open/popup functioning.

I'd suggest a subscription to AllDataDIY - the procedure is well documented there, and I've done it several times myself - PM me if you have questions.

Hope this helps.