Pretty simple actually. If you have power, and you can get sunroof open enough to remove sliding panel just close the sunroof enough to unscrew the two halves of the cable bracket from the transom. Then just hold the cable and be prepared to have the cable feed out with power. Prepare for your interior with old bath towel to coil up dirty greased cable or perhaps a pillow case. Be creative and protect interior from dropping cable. The motor pushes the cable right out, and a new freshly greased cable goes right back in much the same way. Its been a while, but at the end of the travel of the cable, the motor may stop naturally but the cable doesn't come out. You have to access the trunk motor and pull out the white (IIRC) knob to separate the worm gear from the last 3 or 4 threads of the cable then she slides freely. My 91 C126 and the donor C140 capsule in the C126 both had hard plastic wrapped cable like a barber's pole. Over time it swells or gets jagged due to poor lube and jams. The replacement cable is better and completely sheathed as a design improvement.
No power means manually cranking motor by hand and that gets the shoulder and lower back burning very nicely. If searching at a yard for working motors, I bring a motorcycle battery and some homebrew leads about 3 ft long.
