I did one, seemed pretty simple.

Start with the sunroof panel in the fully closed position.

With the panel down, remove the two bolts holding the cable to the carrier frame.

In the trunk, look at the two knobs on the motor/drive. One is round, the other hex. Pull the round one out until it pops into the outward/disengaged position.

You can run the cable out manually, using the hex drive, 17mm (lug wrench size) if the clutch isn't set too tight (many are too tight). In this case simply rotate the hex until the cable is far enough out that it is disengaged from the drive, then pull it out from the sunroof end.

I installed reverse of this, lubed and fed the new cable down into the tube until it hits the drive, then turned it down to the point where it lined up with the bolt-holes that secure it to the carriage. I bolted it on, pushed the round knob back into the engaged position, and all was well.

If your cable was broken, extracting it might be a little more difficult. You will also need to adjust the stop point of the sunroof, which seemed quite easy also IMO:
My method was to run the sunroof closed using the switch. It will stop when the stop-position is reached in the motor. Then I pulled out the round knob, ran the sunroof to the proper closed position using a wrench on the hex, and re-engaged the round knob. Worked great, ... the manual was at home and I was in too much of a hurry to go home for it, so I created my own method.

Another thing: The hex-shaped plastic hides a smaller hex and a lock-nut. This is the adjustment for the slip/clutch in the system. If it is too tight (sounds like yours is if it broke the cable), adjust it.

Disclaimer:
The manual probably has a more precise 30-step process for this, and it is most likely better than my method in some way, you will probably be ahead to read and follow their instructions. This also is from memory, ... your mileage may vary.

Another note: If the whole thing won't work, you can reach the two bolts securing the cable to the sunroof carriage through the tip-up vent panel. Use something to protect the headliner material as you work, but it is a way to manually open the sunroof and then the interior panel if the cable is completely bound up or otherwise unable to move the sunroof panel.

__________________

Gone to the dark side

- Jeff