id use a multimeter to trace the currents down the wires, see if u got a break somewhere and track it back to the fusebox, i had to make my own wiring from scratch for my mk2 but if u can get ur head around the wiring u should b alright.
as for the metal bracket.. dont remove it, the hole in the middle of it is supposed to sit the rubber bung on the back of the head unit so that it is fitted firmly and wont skip and jump so much, it also stops u trapping wires!