That is largely because it is dead simple. I am fairly sure there is a DIY around here somewhere, but replacing the stereo and speakers are simple enough that people do not really need to write it up. The only piece of advise you will need is this: The front speakers need to be fairly shallow to clear the window. The rear, you can go nuts.
My cars have two different speakers for the front. The RS30 has Infinity 6032si using the adapter ring that came with the speakers, and the Blitzen has Kenwood KFC-1665S speakers that mount straight up without adapters. Both sets are sufficiently shallow.