here is a vid of the guys from RvB or atleast one of them doing vid master http://achievementhunter.com/archive/?id=885 all nine hidden skull can be found in this vid done by gav another rvb staffer http://achievementhunter.com/archive/?id=376 hope this helps i don't have an xbox so this is the best i can do
I would burn myself, cut myself, jump off a 50ft high building, and then buy army gets a tan and play that 24/7 non stop before i ever play halo 3 again.