Can I use my current Guild Wars 2 account to log into the game through Steam?
No, if you have a Guild Wars 2 account which was created through the Guild Wars 2 website, you cannot log into it through Steam and vice versa. You will need to continue playing on your account using the client from the Guild Wars 2 website. To be able to login from Steam, you must create an account via Steam and use the Steam client to log into the game.
Annnnnd all hype lost.
You had better pay your guild dues before you forget. You are 113 months behind.