.3ds only, i copied the savs from the old sd card to the new microsd card.
i used the new wireless microsd data management feature described in the gateway manual. i made sure the n3ds would not update, so i launched the system config, added the AP, did the wireless thing and deleted the AP again without leaving system config.
i don't know if forced update are a problem on the n3ds, since gateway did not mention anything about it.