How hard to install a deck in a door

By the time you run all the RCA cords and antenna wire into the car, that's going to be quite a bundle of wires to deal with. There may be some other options, although not exactly what your friend is asking for. --Mount the actual deck hidden in the car, like under a seat, but mount the faceplate in the door. You can carefully extend all the wires going to the faceplate....some radios will tolerate a longer extension than others. I think you can find an example of this at www.installer.com. --Buy a Sony radio, for which you can buy a separate control panel, designed for boats. Mount the control panel in the door.