i had the same problem with my driver side headlight. you dont need to remove the bumper as me and my buddy replaced it without removing the bumper. it was a pain i would recommend removing the bumper if you are replacing both headlights. we were able to remove the driver side tire and go from the bottom of the car and wheel well but it was a frustrating process and may be easier to just take the bumper off
1. Condensation/moisture under the lens. Caused by a bad seal or hole or crack.
2. Fallout residue on the outside of the lens. Makes the lens look cloudy. It's caused by pollution & neglect. If the lights are kept protected with your paint, it doesn't happen. Some places call the removal "scaling".