I was trying to figure the same thing out when I ran across your post. I tried that, but in my case it was easier in the end to just hide the old picture and add the new one in its place. I can always delete the layer that contained the old image if I feel like it. We used to use Photoshop to create our department flyers… it’s way too complicated for our needs, so we’ve since moved to In Design. I had to edit an existing flyer for an annual event, since I didn’t want to create the wheel just to change a little bit of text and the new presenter’s picture, LOL!!
Good luck to everyone else! Photoshop is not the most intuitive program in my opinion.