If you pull the seat, right at the point of the relay section are two large black wiring masses. I cannot remember which side, I think the left, but if you roll the black rubber back, you'll find a rather large size plug, about 1 1/2 inches, white. That's it.
Wait until he installs the CB. Ten to one he'll get the CB error. I've lost track of how many get that one, as did I !!
If the manual was worth it's weight, it would have the pin outs for the CD plug and then we could interface other CD's or MP3 players!! Of course, if you were good with a meter you could do it to I guess.