Having it wrapped wouldnt decrease it, it'd be classed as a styling mod so would increase it i imagine,  Insurance wise, because the car colour isnt permanently changed they dont need to know ( i think) 
  
I think the insurance company will need to be notified 
  
Yes the insurance company would indeed,  dene got stopped the other day for having a rear light out and they asked why it was a diff colour after putting it through the system and he simply showed them that it had been wrapped and all was ok