grab it and shake it up and down a bit.. mine got jamed but with a bit of force i got it on the runners again and has been rolling ever since
from what i can read in this tread buddy i dont think its a replaceable job ie whole new/ secondhad jobbie and to be fair buddy its not that hard to get the sunroof mechinism out if i remember rightly when i wanted to regrease/ clean my old sun roof gttdi you take off all the pillar moulds off then take off all handles and light then take out the head lining and then im sure the is only about 8 blolts holding it up.... may want a friend to take the weight so it comes out nicly