Wow, I just joined this site to get the very same information that you are looking for. But maybe I can help you and get the more knowlege abled members to concure. As far as I can see the Nav unit and face plate must be removed to facilitate the VIAS install. The directions can be found here. http://www.clublexus.com/forums/showthread.php?t=156160
Once that is achieved, you then follow the directions that VIAS has in the box for the wiring harness.
While I was in there I was also going to take care of the DVD fix to watch the DVD while the car is in motion. The fix can be found here. http://www.clublexus.com/forums/showpost.p...mp;postcount=44 Also more good info could be found here. http://us.lexusownersclub.com/forums/index...showtopic=33377
As this is my first post, I hope this was good info.
I am going to try this right now, so maybe I can get some pics and other info on here by tomorrow