I'm changing my drivers side window motor and when I took off the panel the plastic vapor shield like thing inside the door was pretty messed up. Do I need this thing? If so, is it possible to buy a new one?

 

As far as I know the dealer still has these. If your car doesnt see rain/snow/moisture in general and is garaged, I wouldent worry about it. If it sees anything like that then you might have a problem with water destroying the metal parts in the door.

 

It doesn't see those much being in Tucson, but occasionally we can have our moments of rain.

 

I would fix it, to be correct. But considering your humidity is below 10% and you dont see much rain, you can get away with not fixing it.

 

True, If it were me Id fix it just cus it wasnt...

But its not a huge deal, not going to leave you stranded in the breakdown lane of the local highway anytime soon