Lens Cover Will Not Open

A friend gave me a Canon Vixia HF S100 (basically the same as the HF S10) that she was going to throw away because the iris lens protection cover will no longer retract. I don’t know if she dropped it or damaged it in some way, but all other functions seem fine. If I physically retract the lens cover, I see a perfectly good picture on the LCD screen. I have not been able to disassemble the camera sufficiently to access the worm gear that drives this lens cover. I need instructions for disassembling the camera to access the worm gear, and I will likely need guidance in repairing or replacing that assembly. If you can just point me to instructions to disassemble the camera to get to the worm gear, that would be great.

Thanks.