The 13-pin output won't go straight to an amp. It has to go through a floor unit, either a VB99, a GR guitar unit or an SY1000. Depending on which one you pick, there may be a separate output socket for just the on-board guitar pickup signal.
You could use a jack lead from the socket on the bass, but then you have the problem of 2 cables running from the bass to different locations.
If I were you, I'd give it a try with an external kit first. If you buy a second-hand unit you won't lose much money and you can find out whether it works without altering the bass. The divided pickup can just be stuck on, you don't have to fix it down with screws.