So when I've considered buying the Dragons POD, I notice that it says it's a six player scenario of "expert" level. I'm trying to understand what makes it "expert level" when it's simply new house cards.

It's not "simply" new house cards, it also includes new setup instructions. You only play for 6 turns instead of 10, and it follows the plot of the books to start around the begining of Feast for Crows/Dance with Dragons. It's sort of like the first four turns have happened on their own already, and you're coming into the game halfway. Each plyer starts in a potentially disadvantageous situation, and it's immediately a game where the politicking between houses is crucially important. Mistakes are much worse to make in this version as everything is so cutthroat so fast, and for a new player it would probably be overwhelming, but for an experienced player it can be very interesting.

Oh. Yeah, I wanna do that. Thanks.