MillerPKA

Apologies for the lack of explanation I'm really busy and only had a couple minutes to diagnose the problem. Tried opening my sunroof and after beginning to roll back it stopped. I put it back up and looked above the headliner and there is a plastic piece running the width of the car, maybe 5 or 6" wide, that's came loose and is blocking the window from moving along the tracks. I couldn't really see where it should have been in the first place, only that its completely loose. Anyone have any idea what this is, I'm guessing I'm going to have to remove the headliner for this fix. How easy is it to remove the sunroof window? Thanks for any help in advance.