I've put considerable research into this (I was looking to put a mini in an iMac G4) and I can tell you that it really just won't work. I haven't seen any adaptor for the internal connection of the iMac to its screen, so it would be better for you to invest in a display as opposed to stealing from the iMac. I'd say if you wanted to still use the iMac, just set the mini to allow screen sharing and have at it.