I have to make a decision regarding what approach to take to fix some damage to the door of my 2003 330ci convertible. I was backing up and clipped the bumper of a friends car which was parked diagonally behind me. It left a crease about 3 inches wide across about 20 inches of door. I have gotten repair quotes from Master Crafters in Rockville MD, and another shop in Gaithersburg MD, whose name eludes me at the moment. MC would repair the door panel and shoot approx 1/3 of the car for around $1200. The other guys want to replace the door shell then shoot 1/3 of the car for around $3K. The car is Titanium Silver. I can buy a door shell from MileOneParts for $576. I am leaning towards buying the shell and replacing it myself then having MC shoot the car. My questions are: 1) is this very difficult replacement job? 2) do body panels come pre-primed? 3) does the shell need to be painted before assembly? 4) anything I should be aware of prior to starting down this path?