I believe you can just rock up and take the PADI IDC, which is a 1-week course, then you will be an AI, then the PADI IE, at which point you will be an OWSI.
Be aware tho' at this level it is not about diving, it's about knowing and being able to teach "the PADI way" so you may have to relearn some things. It would be ill-advised to try the IE without doing the IDC first.