I wouldn't bother to change the diaphragm if the holes are small. If you want to recoat the diaphragm, clean the diaphragm with alcohol or acetone. Make sure there is no dust on the surface. You only need to coat the the diaphragm one side. It's normal to see that the diaphragm is glued to one of the stators. Actually what you see is the diaphragm glued to a spacer which is glued on a stator.
Can you take some pictures to show us? I don't understand what you meant by a large foil ring.
Best regards,
Wachara C.