The recommendation I would use for this sort of problem is to know one point of the plane before and after the rotation and then use the formula n . (r - r0) = 0 where r0 is a specific point on the plane.
You need to specify how you rotate the plane, but that technique should work for any rotation.
If you are rotating the normal then it seems that you are rotating the plane about some point on the plane and if you rotating about this point, then this point won't change at all since it will have the affect that is at the origin and rotating a point at the origin leaves it unchanged.
If you give specific rotation/translation/etc information I can give a more specific response.