I had the same CD based Navigation system installed in my 2000 E430.
I had Steve Krabbenborg install mine. He has a website,
www.mbenznl.com .
He has done thousands of these installs, all over North America, Europe, and even Australia.
I asked him if a retrofit to a DVD based was possible, and he said no.
I think the exact same information that is on the DVD is also on the CD's. The only difference is that all of the maps fit on one DVD, whereas it takes 8 or 9 CD's to fit the same info.
I live in Southern California, and the level of detail is great. Also know that the CD's are updated with new information, streets, yellow pages info, etc. every year. You might have an old CD.