You're about 1/3 of the way there. My wife has a 2004 Lexus RX-330. To do it right would run about $1,500. That includes all the dash kits, adapters, labor and a new head unit.for $500, you're on your way to buying an OE type backup camera/navigation screen upgrade for your radio. i'd rather have that than a license plate camera.
i have a backup cam/navigation in my truck and use it all the time. i can't backup my wifes camry for the life of me. always looking at the dash for the camera.