Used JDM Hazard Switch, SVX adapters, extra cable for head unit to hook into the g510 for all sound of the nav. Using the nav sound ouput and the sync line right now. Next I am going to get a real g510 cable and try for video also.
outcome is full integration of everything. Watch movies on factory nav, g510 with traffic on factory nav, sound output with mute through new Head Unit. Head Unit has ipod, dvd, usb, sirius.