ok so was the aftermarket unit your purchase for a sd 500
as yes there are differences in the wiring for the front display console and other wiring will need changing also
so i would think yes the wiring may need to be turned back to the cd400 set up
now a trip to rusty may be more helpful to you as pins etc are required
but really you should have got an aftermarket unit specifically to replace the nav500 not the cd400
rusty is your best bet here for help
as yes there are differences in the wiring for the front display console and other wiring will need changing also
so i would think yes the wiring may need to be turned back to the cd400 set up
now a trip to rusty may be more helpful to you as pins etc are required
but really you should have got an aftermarket unit specifically to replace the nav500 not the cd400
rusty is your best bet here for help