Roger, the Bullitt fuel door is not aluminum. It is chrome plated steel. The texture on the outside looks like aluminum.
As far as installation, you have to take the whole door assembly off for it to fit. This includes the cone thing around the neck. it is VERY easy to take off: Unscrew the one screw holding the cap lanyard on, and with the door open, rotate the entire assembly clockwise about 15 degrees. Then it pops right out; door and all.
