Actually, I don't think it's possible to play new leaf online unless you've already downloaded the game updates. I tried updating a few days ago. When you click the update button, I think it redirects to the eShop since it prompted me to update my system. Currently, 8.0 doesn't work with emunand, and you can't access eShop on older versions.
EDIT: Either way, if the manufacturer is wrong, you can change that without losing your save. If you change the Chip ID, it's fine. But if you change the Cart ID, the save will no longer work.
EDIT: Either way, if the manufacturer is wrong, you can change that without losing your save. If you change the Chip ID, it's fine. But if you change the Cart ID, the save will no longer work.