I didn't need to do anything but "shim" the neck (SJ) pickup towards the B string to pick it up better. But if get your hands on just two LJ (bridge) you don't have to touch a thing.
As far as electronics, I originally used the bass/treb (can't remember what the three letters are) EQ from EMG. I had to add one extra hole for the treb pot thats it, the rest fit. If I would have went for the stacked one I wouldn't have needed to change a thing. Heck if I were to do that one all over again I would have went stacked bass/treb, blend, vol instead of vol, vol, bass, treb.
For 18v I use 6 CR2450 lithium coin cells (largest 3v coin cell made I think). Expensive yes (12$ for 6), but so far around 300 hours and the pack still tests around 18.5v. if you stack them 2 columns of 3 cells its about 7/8 the size of a single 9v. I had to wrap each stack of 3 in shrink wrap and then bridged one side of each and brought the other out in a 9v battery connector and shrink wrapped the whole deal again. Viola, 18v, stock compartment, no routing. BTW each CR2450 has more mAh than an alkaline 9v, 600(9v) vs 660(CR2450) I believe.
The only routing I did to my BBN was to add the EMG40 series.