I realize this thread is old, but as I believe forums are the key to loads of important information that would be lost otherwise, I wanted to share the photos and more detailed instruction of this process that I took today with y'all. They're hosted on NICO, where I am a moderator.
If anyone is interested in details and photos for the above mentioned process, follow the link here:
http://forums.nicoclub.com/how-to-retrofit-aftermarket-speakers-into-stock-locations-t597998.html