This is a old post I know but, I am now looking into the same thing.
I have a 2007 LS460L... the navi was never been updated so it's the first image. I have a laptop with Techstream 12.000.xxx and in a day or so, I will have a Lexus labeled USB drive with the navi update for 2013 that I found on ebay for fairly cheap.
I am trying to see if it's possible to use MY LAPTOP, with the USB drive with the navi update WITH OUT visiting the dealer.
I know according to a thread over at Clublexus, it needs some Lexus Installer program. Does this come on the USB drive, or is this on the master CD that goes to the dealer, if so, is it possible to get the app.
Anyone attempt to do this before with ANY luck ?