How do they work? Im thinking of getting a set of EMGs for my les paul, but i don't know how easy they are to install.
if you get the new redesigned in the black box, theyre extremely easy. the only thing you have to solder is to the toggle switch, everything else quick connects. you can do all of it in about a half hour now
i think the little black box should fit in a les paul.

The routed area between the pickups and the control cavity (where the pickup wires go through to the control cavity) is small in my ibanez. So the guy who installed the emgs had to cut the emg wires, so he could fit in the quik connect in the guitar.
Ibanez RGT42DXFX with emg 81/85
Schecter C1-Classic
Vox AD30VT
Knock off P-Bass