Oak:
Though different models, your MB and mine share the same motor.
I've had my PS pulley off. The 3 bolts come off by loosening counter-clockwise.
I'd replace the "11mm" setup with the real bolt that uses a 13mm head. You can look up that bolt(photo included) at this sites parts site. I seem to recall it's about $10-$15.
Here's a pointer to a site with online MB repair information:
http://mb.braingears.com/