I am getting confusing information from my dealer on how to update my 2008 ES350 NAV Map. The dealer says, " purchase the new Generation 5 ver 8.1 DVD and replace the old the DVD, using the control buttons on the NAV screen. Well I haven't bought the DVD yet, but I tried to remove the DVD from screen controls, it shows a DVD screen, with a remove button, but indicates there is no DVD installed. So how does this work? Bob Mack