From what I can read on the site the unit you have in standard form only plays dvd's the navigation is done through an additional unit which will be buried in the dash somewhere and is connected to the main unit, it's this that has to be updated. The M300 uses the navteq maps, is this what you have (should say somewhere on the screen)
It's a bit similar to the system both mark and I have in our vans, the jvc headunit plays dvd's but to control and play an iPod you had to add an additional unit. If you bought the alpine with the van to include the navigation then you probably are not going to be aware of how it's done only that it works.