FAQ: Can I delete/replace maps from/in the Quests memory?

You cannot delete maps from the 115/243Mb memory of the Quest. There is no need to do that, since it won't speed the Quest up and doesn't make room for more waypoints or tracklogs.

You can't replace single map chunks either. The Quest and MapSource don't have that functionality. You can only replace the complete mapset from the Quest by uploading another mapset.