If the motor runs but the roof won't open, more than likely the cable has
hemmoraged out of the tube. If this is the case, replacing the cable and
trying to close up the split in the tube is a waste of time and money. Been
there, tried that..... a few times with customers that did not want to fix
it right the first time.

From the inside, gently stick your finger tips between the front header and
the edge of the sunroof liner. You have to pull it down enough for the front
edge clips to disengage. Then slide the liner all the way back. Now look at
the cable where it comes out of the casing and connects to the lifting
bridge. Is it bowed out and you see the white nylon slides on the cable?  If
yes, you need a new cable and casing. When it hemmorages out of the casing,
it runs past the gear drive of
the motor. To replace the casing, you will need a glass shop to remove the
rear window. Then you drop the headliner down from the rear. The casing goes
into the left rear corner of the trunk.

#607 here in SA 56 167:
http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=126022&M=110%2E987%2C989&GA=722%2E30
0&GM=716%2E007++++++++++++++717%2E402&L=765%2E706&cat=287&SID=78&SA=+56167