Hi all. I am interested in buying the black mirror housings for when my new A Class arrives. (I couldn't afford the £1,000 night package option !) The part number is A2128100079, and I have taken this directly from the Accessories website http://www.mercedes-benz-accessorie..._home/mba/home/accessories/configurator_.html My question is: Are these designed to fit over the top of the existing (body coloured) mirror housings ? Or are they meant to be replacements ? If they are replacements, does anyone know if they are difficult to fit ? Thanks ever so much.