I'm pretty sure all you need are a pair of needle nose pliers. Just squeeze the two tabs together on the inside and pull the sight out from the outside of the slide.
Unless you have an aftermarket sight that is made of metal and is screwed in. Then it's just a very small nut that needs to be undone. If you are installing a new sight that uses a nut, make sure to use a very tiny drop of locktight to keep it in there.