You have untill 5 days before you arrive to make that change. I would advise waiting a little while longer just in case you get an email or postcard or if by chance they release general codes. If you switch to a package now and you get some sort of code either by direct marketing or a general release, if it is within 45 days of your arrival you will have to pay a change fee in order to add it to your ressie. This is only true of a package, not room only. You can make changes to a room only ressie any time but with a package, if it is within 45 days and you make a change that affects the price (ie adding dining, adding/deleting days, changing resorts or applying a code) then yuo are hit with a $50 change fee. You can convert from room only to package pretty easily so I'd advise staying with room only for a little longer. As you get closer then you can make the call to convert to a package and add dining at that time just be advised that if you convert it with less than 45 days to go, you'll still have to pay the full balance immediately since you are less than 45 days out. You won't have the change fee though.
I see you are at the GF, from your counter it looks like maybe your dates are past the current AP rate release but you will more than likely do better with getting one AP and using the discount for the room. You could also get the DDE card and have some savings on dining.
Hope this makes sense!