Hi Les,
Yes, you are correct and have a Generation 4 navigation unit. The upgrade procedure if very simple and basically consists of removing the old DVD and installing the new DVD, and then waiting as it updates the software on the navigation unit.
Unfortunately, the only disc to contain Hawaii information is the Generation 5 7.1 navigation disc and hard drive based navigation units.
I have a 2004 Rx 330. I was told at the Dealership that if I buy a dvd on ebay or something, there's no way to tell on the disc if it's the correct one for my car. And they said if I got the wrong one, it might crash the hard drive. Is this correct? If not, what's the latest version that would work for my car?