So I just bought a NAV HU from a 2012 Subaru Imprezza. It looks like the ones that would have came with my car if I ordered it. Am I safe to assume it's plug and play in my car? Do I need to buy GPS antena or something? I have the 20 pin combined harness from SVXc that was going to be used for aftermarket amp install. Can I just use it to connect the NAV unit to my harness? Just want to leave it in the car so I don't lose it.