I don't know if you want to do it yourself, or have someone do it for you. If you want them cleaned thoroughly try using one of those services that clean home duct work. I'm sure they can do it right for you. They will also know the best way to mediate mold if that is your problem.
Tony & Ruth........... FMCA#F416727
Newmar Dutch Star 4320, Spartan MM Chassis, Cat C9, Jeep Grand Cherokee,with Hemi, hooked up with a Blue Ox Aventa LX, and Brake Buddy.