If you already have a Gamer Launch account connect your Facebook account on your user profile first before using Facebook connect to login. Otherwise you may end up with a new account.
Give those level 90 alts you left behind in Panda Land a quick boost to 100 by following this WoWHead guide.
Note: There are some requirements in terms of actually opening up your level 1 garrison, flying achievement, potions, gear, and so on. But, they're doable.