My motor already had a gear attached, but it was tiny and would have caused some issues with a normal 3d print. For the matching gear, I halved the extruded line thickness on the outer edge, to ensure tolerances were ok. Worked fine. For the remaining gears, I used a larger set of teeth, so tolerances were not an issue.

Put them together, check they mesh well enough. Fit motor in, and fit the socket into its carriage.

Program arduino with the included code. Easy enough with an Arduino Nano. 

Connect as shown in wiring diagram.

With any luck, it will flash a few times and then retract the socket, turning itself off. Congratulations, you have successfully wasted your time and built a useless machine!

:-D