Just changed the cable for my sunroof last week and it was an easy job, if you have the cd's if not i'm sure we can talk you though it!
Once you get the headliner out you will see if the cable is bent or broken. Mine was all bent up. You will also see if everthing is sliding the way it should be. The headliner came out and went back in very easy. The cable was a little pricey about 100 cdn. or 45 us.