replacing aftermarket stereo with monsoon

My brother has a 2005 GA that came with a monsoon deck. I have a '96 GA that came with a cheap aftermarket deck. Would it be possible for me to replace my aftermarket deck with his monsoon deck without screwing up the anti-theft system either in my GA or the deck. Do they work together or are the anti-theft systems universal on GA's? What would I need to do to be able to use his monsoon deck?