Exactly what I did some time back on the 300D -- someone had glued the sunroof shut before I got the car, and the PO had it opened up to estimate repairs. Bridge stuck sideways, etc.
I got mine to move (after pulling the liner out from underneath) by twisting the bridge and using the hand crank. Big PITA for something I never use -- not a sunroof fan.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!