Many thanks, that helped.
I found the reader and managed to replace the old disc (07/08) with the new one, but now I get a funny behaviour on the display:
The "Map info" seems to recognise the new DVD, because it shows the area, coverage and year (10/11), but when trying to navigate, it says that the maps can't be read.
Is anyone aware of whether some sort of initial setup is required, when upgrading?
I borrowed the new disc from a friend, because before spending my hard earned money I wanted to check if the upgrade is really worth it, but I can't keep it forever and would like to check it ASAP...