Rear sunshade troubleshooting

[mbzman]

The sunshade/rollerblind has stopped working on my 300CE. It was operating quite slowly and had difficulty extending fully. I heard a loud crunching sound when it was being retracted and then it would no longer raise. I listened to see if I could hear it working while pressing the switch to raise it but I do not hear the motor working. How do I get access to the shade mechanism and how does the device operate?