1999 speedster sk stereo question

[Rock21]

i want to put a stereo in my speedster SK and i was wondering if there was a certain location to mount the speakers and the deck and if there is wires already in the boat to wire it up if i use the correct location. meaning a positive and negative for the deck and speaker wires because some boats had the radios already i them i didnt know if they came prewired. also is there any special way to make cuts in the hull and mount the deck and the speakers. hope someone can help. thanks allott.