I was wondering if anyone could tell me where I can get instructions to replace the GPS unit in the trunk of my car? Any help would be appreciated.

 

Using the search...Advanced search tool at the top of the page will find a few thread about taking the trunk garnish apart so you can reach the NAV ECU ....referred to by most as a DVD player. However, what is the end game with your project as the NAV ECU is integrated into other components such as your dashboard controls and ML amp...
Regarding the Advanced search tool...narrow the scope of your search to the SC430 forum will help to find the info you want more quickly.

 

Do any owners not do updating of units or software discs and just buy the latest greatest Garmin for $100-200 and stick them on the windshields?

 

Well that is an option of course. But I believe many are comfortable with the in dash and integrated NAV system, and would prefer not to have an additional device stuck to the windshield. While the Lexus NAV system has its shortcomings, having it hide-a-way nicely behind the wood paneling with a push of a button is a nice touch.