Hey all,
here's the section from the 1989 galant tehnology manual that shows how the sunroof mechanism works:






Hope this helps,
It, sounds like a cable problem. pull the side trim unre the glass and there are 6 nuts holding the glass to the runners, Pull these and you can lift the glass out. Drop mthe interior light and you can pull the sunroof motor and gear assembly. then you can manually run the side lift brackets eithe rside both for ward and backward and check out the linkage from up top, and throught the motor pinion hole underneathe you can check to see the cable has all its teeth intact.
Hope this helps,
Rich