You just go to Gharaffa immigration with your Interview letter and show them. then Some times they will allow ur wifes visa extension two more weeks. and after Interview, if ur Family RP has approved, it will be declated within 3 days. once it approved, then you can proceed all the formalities without your wive's exit. and i think hardly one or two weeks required to complete all these formailities. but once its approved, you can stamp one temporary visa from Gharaffa Immigration. best wishes.