Yes, this mainly is correct. BUT i have bought only the europeen navdata, not the navdata for the hole world. I don't know if the worldwide-data will also work, because at the worldwide-data there was an specific "GDU-version" required - i don't know whats this means. And of course, the worldwide-data is mor expensive (about € 90).
And the really fine sideeffect was, that there was also the newer navdata-format included, which work wich the GTN.