I used this motor that I got off Ebay: 12V DC 60RPM High Torque Gear Box Electric Mini Motor | eBay
I had the switch which is a DPDT momentary contact. This can be ordered from numerous sources.
And I got the two limit switches from Radio Shack.
I cut the original handle and used only the part that slides onto the vent actuator. I drilled a hole through the part that the screw was inserted in and through the motor shaft and used a finishing nail as a connecting pin.
And the conduit from Lowes or HD.
I used bailing wire connected to the metal part of the vent to actuate the 'UP' limit switch and part of a hose clamp to actuate the 'DOWN' limit switch.
And here is the schematic