You shouldn't need a dash kit if all you're doing is replacing the HU. As far as getting the factory piece out, look for four small holes, two on each side, towards the corners of the face.
Now, you can either go out and buy a "Ford Radio Removal Tool", or you can get a wire coat hanger, cut it so that you have two "U" shaped pieces that will fit into those holes. Either way, you insert the ends of the tools/hanger into the holes all way (you should be able to feel when the catches release), put some outward pressure on the tools, and pull the radio out.
