Joe, he's beautiful, and I agree with your I.D. of Chromodoris ssp. I have to support Acrid on this one, Nick Dakin, in his Complete Encyclopedia of the Saltwater Aquarium, has the following to say on Chromodoris ssp.
"although commonly available and among the cheapest of sea slugs, their life expectancy in captivity is short . . . All are predatory, feeding on a wide range of sessile invertebrates, from sponges to barnacles, sea squirts to soft corals, and most seem limited to just one prey species.
I've tried a couple long ago, but gave it up when I couldn't keep them alive over the long run. They usually lasted a couple months, and I assume eventually starved. However, as the others also said, the LFS seldom has any idea of how to keep these alive, and seldom has a reef tank with sufficient biodiversity to support them. Personally, I'd probably put it into my reef and see how it does, confident in the knowledge that it has a much better chance in the greater biodiversity of my reef, than in the limited biodiversity of a LFS display tank. Good luck with him!