Wanted to help my buddy install his Custom Sparky long distance, and someone else sent me a PM asking how hard it was to do. Figured I'd post it here in case it can help anyone else.
I used a 1/4" nut driver, a 5/16" nut driver. and a Phillips screwdriver.
Step 1. Take the balls out of the game. Pull your playfield out and rest it up against the backbox. Protect the backbox if you're worried about denting or scratching the T-Molding. Now remove the 4 screws that are holding Sparky from the bottom of the playfield.