OK than...
regarding the manual you should be fine at least concerning the additional maps !
dono about the speed for the card, but any should be ok, as long you look out for the storage size of it, which the unit can cope with... (my 60Cx can take up to 8GB, the miniSD containing the NT-2010 maps only needs 1.8GB and the pre loaded maps on this miniSD cards is 2GB only, just to have some additional space to fit some tracks too)

your purpose seams reasonable to me... to make live a bit more comfortable that's OK...

so.. dose the unit has this City navigation-NT 2010 already installed, or did you just read that of the box ?
in case the unit is equipped with a miniSD you may only got a 1GB card in it or less, with no maps at all, in that case you are running on the world basemap I presume...
in case you got the city navigator-NT 2010 DVD sold with the unit you have to buy a empty miniSD card and transfer all the maps to the unit with the sd card placed in to it, or use a SD reader if you got the miniSD adapter card that got the size of a std SD card.

Now just to let you know... the process of transferring all European maps to a 2GB miniSD last some 12 hours ! one reason why I bought the Garmin miniSD with the pre loaded maps in the end and not the DVD !

Well you where on about that you would like all maps like the European and eastern maps on your unit... well in that case you have to buy either both pre loaded miniSD and swoop them as you go, or you have to get both DVDs install them and transfer all maps to the unit at ones. because all maps will be stored as "one" file to the miniSD, the mapsource program is recompiling the lot together and sending it to the card.

check out what is installed in the unit, there must be a point in the menu that is showing you what maps are active and you may find out that way what part is missing that coursing you headache...

spooky

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The trouble is that he was talking in philosophy, but they were listening in gibberish.