In order to change the left wing mirror on a Subaru Outback 2003 you need a flat screwdriver, a star-shaped screwdriver (Phillips) and an 8 mm socket wrench. To get the repair done, you have to follow the steps below.
In the beginning, you have to pry out the plastic pin situated on the right side of the door panel, the one situated on the left side and the plastic part surrounding your door handle using the flat screwdriver, as shown in the picture below. Be careful when you try to remove the switch panel of the door. We recommend you to pry at the bottom at first, and then at the top, using the same screwdriver and maybe a cloth to protect the parts against scratches. There you will discover two harnesses that you have to disconnect.
Do not forget to remove the plastic triangle on the upper side of the panel by inserting the screwdriver between the metal on the door and the plastic. It should pry out easily as it is held by three small plastic pins.
The next step is to remove entirely the front panel of the door. You will be able to do that after you unscrew the two Phillips screws situated on the middle side of the door panel, as in the image below. Then you have to pull firmly the plastic panel of the door towards you, until the back clips have detached.
After you have detached the door panel, there is only one connector that you have to pull off.
The final step is to unscrew the three bolts (sometimes covered with small plastic covers) that are holding the mirror, using the 8 mm socket wrench. Obviously, do not forget to disconnect the electrical wire of the mirror and you are done.
Be careful when you put everything back together. Make sure the front panel is aligned correctly, up at the door window and at the door handle, and the plastic clips are pushed back in, as it should.