I was playing with my backup camera switch the other night and the GPS back up camera started to work, something that we have not experienced before. The GPS screen looked like an old blue/purple DOS screen and it was asking for a Nav disk to be inserted? Were does it go as I was unable to find a slot. Is there an update to the nav computer that I makes sense as this is a big piece of the dash or is it just used for the back up camera. I may need new switches for the dash, are they Prevost switches?