Yes, that's the way to do it. There is a brief explanation how to do that, it's posted either on E38.org or bimmerboard.com. If the actuator is not working at all, I think that's the only way to go. I assume, you already checked the fuses...
Maybe is frozen. Have you tried to wash the car with hot water and operate it? Or park it overnight in a heated garage?
JOY = BMW