DVD Nav Question

[ZeoStar]

Hi Everyone. I'm new here and my friend told me I might have some decent luck getting a comprehensive answer from there forums rather than others. Here goes...

I somewhat recently bought a used Lexus from a couple who never drove it anymore (2003 GS 300, Nav, heated seats, 5 CD changer, sun roof 33k miles for $30k). I had my friend take a look at the nav system and he said it's a Generation 3 model and that I might be hard pressed to find DVD upgrades for that model. He made me what he calls a "generic" 2006-2007 map upgrade that would work, but not have voice guidance (he was right).

Would it be feasable to try and upgrade the Nav to the latest generation model or would I be better off just leaving it as it is and grabbing a hold of Generation 3 upgrades as they may or may not come along on ebay? I tend to travel to newly developed areas often and I got sick of driving on to a street, but the nav told me I was going in a lake...

Thanks for any help in advance.