Pioneer AVIC Z1 bypass DVD

I just had the new AVIC Z1 installed in my car today. They told me the DVD cannot be bypassed without losing the NAV system.  There is another way but that would be changing the brain of this unit and if you ever had a problem that the unit had to be sent back to Pioneer. They would not even touch the unit once they realize what had been done. The only idea the installer gave me was to add a DVD receiver unit that runs about a hundred dollars and use the AV/input outlet.