Replacing veneer & stain/discolor of veneer (Photo)

I am planning to replace my veneer because of its stain(or discolor as attached pic) and adjusment of veneer shape. Is this stain in front or discolor from inside? If the stain is not removed after bleaching, I will have to replace. Will there be additional grinding/removal of my teeth in order to replace the veneer? Or will it be just removing the adhesive like polishing that will not have effect on the thickness. I am worried since my teeth is originally small, if there is additional