ACK!
i am still awaiting delivery on my copy. making me nuts, it is.
anyway, yes, by all means install it now. there is an area that is added to the current game and then there's the add-on area you must go to before the end fight. i'm in chapter 3, and mine's going in as soon as i get my hands on it.
*sighs* maybe it will arrive tomorrow.
V***V