You'll want to make sure when you purchase your replacement glass that you get a new piece of glue tape to secure the glass. No matter how careful you are the old glue will not be sticky enough or lay flat enough for your new glass to stay securely flush with the camera dome.

I chose to keep the center section in when applying the glue tape. This was to prevent the tape from accidentally getting stuck to the camera. I could have instead removed the circle before placing the tape down and this would have prevented me from having to awkwardly pry it out afterward. Pick your own battle...