I have printed this business card previously, so I know the layout I want and I have the files. What I don't have is Photoshop or any of the other formats used by the printing company, 4by6.
You would use the template provided by 4by6 to layout my two-sided business cards. Once they look good, you would create versions with the same layout for my three co-workers. Finally, 4by6 needs separate PDFs for the front and back of each card. These, plus your Photoshop (or other) files would be the deliverables.