Is there an extra harness interface needed when adding an additional radio head unit in the cubby hole? Or will a 3rd party radio easily integrate with the stock wiring of a 2008? I know with some cars you need a special harness that converts the stock wiring to standard wiring. Then you can plug in any 3rd party radio into your car. Is it the same with the Prius '08? I'm trying to purchase all the parts I need in advance at a lower cost. Then go to a stereo install store to have then install it. I figure if they sold me the parts I need they'd be way over priced.