You may have the same difficulty that I am having. The grinding noise you hear is after the fiber gear that drives the sunroof cable has been stripped.
you can remove the sunroof motor by disassembling the fastners that hold it to the trunk. To get at the stripped gear, pull the plastic manual nut off then remove a metal 17mm nut that holds the gear against the drive cable. Turn the motor around and take out the small fastners that hold the cover of the gear assembly on. It all should come apart at this point and you can get the drive motor assembly off the drive cable. I think the gear either wears out or gets stripped when the sunroof takes too much force to move due to lack of lubrication.