yea im a ford man, so they are my specialty, and my buddy has a shop and all he does is pretty much ponys
the late SN95's(01-04) are the easiest mustangs to work on
you just have to pull up on the trim around the shifter then pull out on the panel that goes around the radio, unplug the trac button (and others) exposing the two 7mm screws at the bottom of the radio holding it in.
mounting the AVIC into the dash kit is super easy, it just screws in, also make sure to add the rear support bracket (one screw) to keep the avic from bouncing around and rattling.
and you already have the wire harness, so you will just need to wire it up to the new harness from the avic, most V6's dont have the mach system so you shouldn't have to do any thing special (even if you did have the mach system it should have been taken care of with the first radio)
do the bypass,
run the mic cable,
then mount the GPS antenna (i would try to mount it below the dash but above the heater vents)
if doing the camera, you will need to run the video cables and tap into the reverse lights (which can sometimes be done near the front of the car or at the light itself since you will be back there anyway running the video wire)
run the ipod cable (if wanted)(make sure you get the right one before the install because most peoples problems are because they use the wrong ones)
then put it all together and be glad that you saved $100 on the install labor
as far as the camera, the key holes are nice and hidden but i really dont like the camera being off center, with some flush mount cameras, you might need to drill the hole out bigger which can lead to rust issues, and if your camera ever fails then you have to find the exact same size which can be a pain in the @ss, i really like the license plate cameras they dont always look as good but they are always in the center and easy to replace if they fail