If you're talking about the trim around the windows.... it's not too hard. I have a coupe so these instructions will be a little different than for a sedan:
For the trim that sits under the front windows: Open the door... and pull it up. It's held in by a metal strip that sits beside the window glass.
For the trim that is under the rear small windows: It is stuck on by double stick tape and there's almost no way you can get it off without destroying it. It's pretty cheap, so just buy new ones. (approx $25)
For the finisher trim above the windows: First, you're going to need to take out the rear windows. Remove the panel that sits in front of the seatbelt pulley. It just pulls off (might need a screw driver to pry it). Remove the arm from the rear of the window by popping off the little plastic cap and sliding the arm out of the bracket. This will make more sense when you start doing it. Then, go back to that panel where the seatbelt was... Take out those two bolts. MAKE SURE SOMEONE IS HOLDING THE WINDOW! The window will just pop out (fall off) now. Now, under the weather stripping all the way around the door/window you will see a bunch of screws. I think there are 14 or 15 of them total. Start at the front and work your way back.
Obviously, to put it back on, just do this backwards.
I have removed them before.
the front and back are easy, just pull, they come off, and they don't brake
The side is a little harder. Take a screwdriver (wrap the end in something so you don't scratch the car)
pry one end and slowly pry the brackets loose. Each piece of trim is held by little brackets, they go into little holes in the door.
You will brake some of them, specially if your car is older.
Go to the dealership and buy a bunch, they are like 60 cents a piece or something or maybe $1. Don't forget the little rubber condom looking thing for the brackets also. like $10 cents a piece.
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