The 12v bible would be ideally suited to the job at hand.
Decide before you start if you want to run two batteries or not,my personal feelings are that a second battery is rarely necessary in a centre console due mainly to the fact that you are not drawing big currents like a fridge,spotlights are used when the motor is running so they arent a problem.Bait pumps draw a bit,but then again my 5m runs on one battery and I have never had a problem,however I dont go offshore.
If you are travelling long distances off shore then I would fit a second battery.
basically an isolation switch should be fitted to the positive line then take your positive from the switch to a fuse or circuit breaker pane,(hint,,,always fit a panel with three or more fuses/switches than you think you will need,because believe me,somewhere down then track you are going to fit something else and youll need a fuse to cater for that),from the switched side of the panel go to the item you wish to control,from the negative side of the item take back to a negative bus bar,from there a single cable back to battery negative.
JUST REMEMBER THE CABLE FROM BATTERY + TO THE ISOLATION SWITCH WILL BE CARRYING ALL OF THE BOATS CURRENT INCLUDING START CURRENT,SO HERE I WOULD BE USING 2B&S----THE + CABLE FROM THE SWITCH TO THE FUSE PANEL AND THE -VE CABLE FROM THE BUS BAR BACK TO THE BATTERY WILL BE CARRYING ALL OF YOUR HOUSE LOADS,HERE YOU COULD USE 8B&S(MinKota cable)
If you have any doubts at all technically get some professional advice or have some one qualified do it for you