I know that the motherboard has died on my radio/ac controls. i am looking to replace the factory unit so that everything is back to normal. I have found several used units in my area, but I am concerned they may not have come from a car with stock Navi. Anyone know if that matters? I'm under the assumption that a radio unit is a radio unit as my navi still works fine even with my current issues. Any help would be great! Thanks!

Wrong forum, but -

Don't replace it with another stock unit, if it's as old as yours, it's just as due for expiration as yours was.

Go aftermarket and cure it for good.