ugh that sucks. if it was a normal deck, it wouldnt have many wires, but since were dealing with a mach head unit and external mach amps that run on 9v system, its going to be a pita.
maybe chiltons/haynes has a diagram of the mach460 deck/harness. other than that, id say save the headache, and take it to a professional shop, might cost but it might be worth not going through the headache.
__________________
-Thomas-

1998 Eclipse GST Spyder - 14b turbo | 3" Catback | Evo8 BoV | 170fwhp if that
2003 Redfire Cobra - 448whp/435wtq - Sold