my rear drivers turn signal/brake light is out on my 2005 cobalt LT. I tried taking the 2 screws out, but the assembly will not move. i cant make heads or tails out of the owners manual. if i pull back the carpet and undo the cargo net, there is a long threaded rod with a nut on it, but i can not get to it becasue the factory speaker is in the way. please help, i really need to relace the bulb.