I did the mod and will do it again with miracle men pickups on my eclipse. There is a ground wire on stock esp's. Its wired in rubber band with other emgs wires. Mine had a black wire, a very fine one coming out of a tiny hole in the body and it was just soldered to other ones from the emg kit.
Its really not complicated to remove and just solder it on one of the passive 500k pots. Best advice I can give is to wire your pots outside of the guitar on some cardbox so you get an almost ready to screw kit. Just put this inside, screw and connect pickups, jack output and toggle switch and you're done.