Not sure what part you are looking at but you don't need to mess with the sight. The TSW models that can be switched over will have a small hole drilled at the rear of the vertical slot that is milled into the slide behind the the safety lever. When you lower the safety lever you should be able to see it. That is where the decocker return spring seats, and if the slide is not already milled for the decocker parts I don't believe S&W will do it.