The short version is, see this page, and select your ML:
http://mb.navigation.com/home/en_US...filiation&acq_channel=aw&utm_campaign=aw&utm_source=Geographic+Enterprises,+LLC for the nav map update - and contact your dealership to determine if any firmware updates are necessary (or even advisable) for your system.
There are two different kinds of updates: One is COMAND firmware. Firmware updates are usually produced on CDs (not DVDs); they done to provide compatibility with new map DVD formats, to provide a bird's eye view, 3-D city views, and ETA (estimated time of arrival). If you have the features you want, then doing a firmware update is usually not necessary. In addition, a firmware update can have tradeoffs: In some years, getting Bird's Eye View and ETA caused loss of the ability to make nav entries while in motion. While making such entries while you are driving is unwise, it also prevents a passenger from doing so.
Far more frequent is the need for a navigation map update. Generally speaking, up until MY 2006, the navigation discs released each year contained the minor software tweaks that provided (for example) different voices for nav commands, and the like. When a new DVD was inserted, the first thing that happened was that the nav software (distinguished from COMAND firmware) was updated; then, the new navigation map data was loaded. In these systems, map data was read directly from the DVD; it remained inserted in the nav reader. Updating map data usually took less than 5 minutes.
From 2007 through 2009, nav map updates were done similarly, except that the map data was transferred from a 2-disc set to a hard drive internal to the COMAND unit. The DVD did not remain inserted. The download time from the DVD to the HD took much longer. I believe this is the system your ML uses. You purchase directly from MB at the link provided, or from your dealer. There are installation instructions with the package.
Beginning with MY '10, MB began using a 6-digit key, generated from a combination of the VIN and the DVD number. One purchases a disc from the dealership (usually around $40); and also purchase a key (usually around $250). Dealers sometimes quote one price for both items. The DVDs are in a 2-disc set, and can only be loaded into the internal HD by use of the key. The update time can exceed 90 minutes, and a battery maintainer/charger must be connected (ignition remains on throughout the process). I do not believe this system is used in your car.
With a 2009 ML, it is unlikely you require a firmware update unless one was released to address particular problems. Your dealership can check service bulletins and let you know if any are recommended. However, despite cost, the best place to purchase your map upate is from MB directly, or from the dealership. At the time of this post, the purchase price id $199, vice $249, and the $30 ground shipping is free until June 30 (saving another $30).
