I am about to do the same with mine. As far as I know, it has to be done via dealer and may need MMI updates to go along with SatNav update. I was quoted £160 for the lot by my local dealer. Not sure there is another way to do it with the HDD based versions.
As your car, like mine is 2009, it may have the 3G MMI, which is nothing at all like the older 2G MMI and the CDs just wont work. Completely different code.