I just did an all grain s'mores porter. I'd just find a base extract recipe for a type of beer you want, then throw a sleeve of graham crackers in the mash, use some vanilla extract (or beans), chocolate powder, and some lactose into the boil.
Mine is still in the fermenter, so I cannot speak to the flavor, but I am kegging it this weekend and I hope it is everything I was looking for.
Good luck.
EDIT: Oh yeah, do not be surprised to see your OG up there. I think mine was 1.095. There's a lot of sugar in there.