Listen, I'm no expert. I removed the 2 cabin lights in the main salon, the 2 in the V-berth, the 1 in the head and the 1 in the pilot berth.
The wires for the 2 in the salon run up into the upper deck where I couldn't get access to them without a major destruct job... Also, those lights had water leaking into them (I found that issue and fixed them)
I created 4 or 5 wooden pads about 5" in diameter out of 3/4" poplar. I drilled a hole through the center and then routed a groove from the center out large enough to allow 12/2 wire to run through it. You can see the pad under the brass light in the picture. The lights are LED white with brass housing.
The one in the picture below had 2 grooves routed in it to allow a wire from the main salon to run to the light over the galley which then ran under and through the access area under the cockpit to my DC panel over the nav table.
For the wire runs I just ripped the poplar into 2 strips, one was 3/16 x 3/4 which is attached to the ceiling and the other was 1/2 x 3/4 which I routed to allow the 12/2 wire to run through it. I stained it all and threw a few coats of gloss on it.
The picture below that is for the light over the salon table. The runs go past the grab rails and then run aft parallel to the rails...