I think you don't have to have the dealer update the built-in Nav. That said, the update costs $150 and comes out every 1-2 years. The build-in Nav looks very nice, but the update process is still out of the dark ages. From some research, it appears that the auto industry is aware of this problem but is moving slowly.
I'm looking at Garmin standalone Navs. Garmin uses a different update process for it's latest Navs. Every few months they publish updates to the software and maps. For example, the nüvi® 3597LMTHD has lifetime free updates for the maps. It looks like there are several ways to do it, but essentially it involves installing an app on your PC or Mac, downloading the maps and/or software to your computer, and then connecting device to the computer. Simple, fast, and free.
Another advantage of this approach is that you can download libraries of POIs or create your own. Once downloaded or created, they can be uploaded to your Nav.
Each approach has its pluses and minuses and I'd prefer a built-in Nav, but I don't like the idea of out of date maps. And it's pretty static. AFAIK, there is no PC/Mac app that can be used to change or add to your built-in Nav.
I've posted about this on other forums and so far no one has been able to provide information that contradicts my findings.
Regards,
Dan.