Hi Ant:
You have the same 4runner like I do...V8, Nav, galactic gray, Air suspension. Congrats on a good choice of vehicle. i.e., 4runner.
I added the CD changer through Soundadvice, an electronics chain here in Florida. They are part of the Tweeter Group so you might be able to do it in other states. They did it for about one third the price of the stealer.
I saw the unit that the stealer had, and it looks very similar to this Panasonic that I added to mine. One was marked Toyota and the other Panasonic. Turns out that Panasonic makes the 4runner audio equipment head units for 2003. It required an adapter from Blitzsafe and a harness from Toyota. It goes in the center console, and fits neatly on the drivers side, next to the coin holder. (That is where the stealer installed one goes as well so I told my installer to put it there. It is easy to use in that location.) They cannot fit in the glove box, the "trunk" area is just plain inconvenient, and under a seat means it has to be oriented with the door to the back, making it vulnerable to being kicked by a rear passenger.
The unit only plays CDs. I guess you would have to get the DVD changer to play video, and I am not sure it can be done on the NAV screen. In any case, the NAV screen does not seem to have good enough resolution. The Panasonic has not skipped on me as yet, and it plays CD/R.
Incidentally, Soundavice told me that Blitzsafe is aware of the glitch in selecting disks on the nav, and they are supposed to update the adapter software to fix this in a few weeks. Soundadvice promised to install the new adapter when it comes in, since they gave me the word that this thing would work. In thinking about this, the other head units (non-NAV) do not seem to allow selecting CDs manually (based on the manual) so this feature might be unique to the NAV.
In a few weeks, I will let you know if the adpter update is real.
I must have been the guinea pig for a 2003 4runner w/NAV non-dealer CD changer install, but so far, I have no regrets considering the amount of money I saved, the look of this thing in the console, and the performance and use that I have gotten so far.