sunroof will open all the way. It will close until it is about an inch but not completely. Functionality is fine otherwise.
Looking down from the top there are no obstructions.
Do I now need to remove the headliner to access the track which I read about? Anyone done this?

 

moved to W164 forum...

 

Had the same thing happen to me on my 2009 ML 350 last year. Seems a plastic piece broke in the track that kept the front shield from pushing down so the sunroof could completely close without undue pressure needed by the sunroof motor. I found that if I reached in and held that shield down with a flathead screwdriver (or other very thin tool) while sitting in the drivers seat and then closing the unit inch by inch with the switch, I could get it closed. Don't know if I'll ever open the thing again until I sell the vehicle. To be honest, I only opened it once or twice a year anyhow! Gets hot here in SW FL and we run the AC all summer/spring/fall so only time I would ever open it was in the winter.