How To Replace Sliding Glass Door Trim . The first thing you need to do. replace your old window or door with a sleek sliding glass door. if you're removing a sliding glass door and replacing it with a new one of the same size, here's how to take on the project. It can be done with the door in place. replacing the glass on sliding patio doors doesn’t mean removing the entire door; trim molding for sliding glass doors should be pre. part of the series: Our guide walks you through each step, ensuring a perfect installation. in this video, how to trim out a glass sliding door