I can't say much of anything about Crutchfield as I ordered it from USA Spec directly, but it shouldn't be too hard for your local guy. I would recomend printing the install instructions (not the users guide) for the Honda MusicLink off of the Fit Accessories section of
www.collegehillshonda.com and giving them to the installer. They cover how to safely remove the head unit without damaging anything... don't bother with the cord placement instructions though... no need to cut the glovebox or anything. FWIW, my test is Saturday so I'm hoping to make a nice writeup with pics after then. Good luck!