Haneda Airport Customs

My flight arrives at 5:25 in Haneda Airport, I saw that the hours of the exchange office close everyday at 6:30pm. I am will be arriving on the 3rd of September with 3 other Americans. We will all be traveling light 1 small carry on, and a large bag that is empty (for stuff we intend on buying.) How long will it take to get through customs? Is it necessary to go through customs prior to exchanging my pass? Overall will I have enough time to exchange my pass? Any information would be helpful as this dictates the flow of the entire trip.