The stop molding around the door holds it in place. Removing the molding allows the door to swing out of the opening from the bottom, and be removed from the track. Once you have made repairs, hang the door (swing the door out at the bottom to engage rollers in the track) and replace the stop, paint trim as needed. It might be possible to remove the stop molding intact if you are careful, but it is inexpensive to buy and easy to cut.