The factory is HIGHLY overpriced on their service. If you are handy with tools, you have the CD manuel. Give Merlin a call at St. Charles Isuzu and price the parts. Will be a lot cheaper. Or if you want to take a chance on used parts allhundaiisuzu.com.
But before any of these I'd buy a can of electrical cleaner, pull the plugs on all those parts give 'em a good cleaning/drying and see if that fixes the problem. Good luck!