Defogger problems of the 2004 Infiniti G35

2004 Infiniti G35 coupe: electrical issue in center of vehicle, the air vents, heat, defrost will not operate and at times come on automatically including cold air and causing film on the dash making it incredibly difficult to see. Was told by Infiniti dealer this exists in over 90% of models this year and type and will be $5,000 to fix. Defogger and defrost vents will not work by manually pressing buttons.