As far as the dull panels, a light rubbing compound followed by a good waxing May bring them back. It depends on what the finish is. If it is gel coat paint rubbing compound followed by a waxing will definitely help.
http://www.amazon.com/3M-Marine-Rest...QNYEB4BWZV5PKY
As far as the decals go, I don't know any way to save them. I used this product to remove stripes from my wife's car which has some fiberglass panels. It was amazing how easy it was. It was like using a pencil eraser.
http://www.amazon.com/3M-Stripe-Whee.../dp/B00063VT0G
With any technique or product, test on a small area in an inconspicuous spot.