I too am back in Skyrim after some time away. I'm kinda stalling now cuz I want to play the DLC before finishing the main storyline[s].

You might be waiting awhile..

EDIT - looks like the DLC - Dawnguard - will be out circa today / tomorrow. Might check the marketplace later on.

for anyone out of the loop the DLC features two factions - Vampires and Vampire hunters with a fat stack of new stuff and improvements like mounted [horseback] combat.

Also the vampires look beastly and powerful unlike the previous vampires of the series..