Retrofit your BMW with the full Navigation system
You can Retrofit your BMW with a full Navigation system, although it is more challenging than just swapping out your display.
I have some of these parts on the following webpages, but do not have widescreen displays for the 3 series or the misc brackets detailed in these part numbers. I also do not have kits that come with all of these parts.
There are a number of websites that detail this procedure and documents from BMW that detail this effort.
Great links of information can be found here
BMW 7 Series
BMW 5 Series
BMW X5 Series
BMW 3 Series - Great informational sites -