Originally Posted by AlexBmur
How important or easy is it to put the plastic that's attached to the door back in place? Also what purpose does it serve?
If you're just replacing the speaker, you don't need to remove the plastic.
If you're adding sound deadening, you won't reuse the plastic anyway, or at least I didn't.
The plastic is attached to the door with a bead of Butyl (you can see some of it left on the door in the photo). You have to tear part of the plastic to remove it completely, but if you were VERY careful, you could remove it fairly intact and reuse it. There is a very thin piece of foam attached to the plastic that is supposed to act as a noise barrier. The plastic itself is probably just a moisture barrier to protect the door panel.