2000 GS 400 Navigation DVD upgrade help
 

hey,
i just bought a 2000 GS 400.
my nav version is 1999, so i know it's pretty old.
i drove to boston yesterday and the map is wrong. i know boston had a lot of road reconstructions.
i want to update my system and i heard that i have to buy a dvd from the dealer. i also heard that it is soo expensive.
i try to look them on ebay and wonder if i can buy any lexus nav dvd. would this work?
sometimes the seller confuse me by advertising that their dvd only work with like 2003 ls/gs/rx...etc...
the latest version is 5.1 right? can i buy this?
i am too busy to go to the dealer.
any thought or suggestion is appreciated.
thanx in advance.