Until very recently, there was no method of transferring all of your 3DS save files, Streetpasses and downloaded content from one 3DS to another. However, thanks to a firmware update, you can now do exactly that. It's simple, only takes about 20 minutes and, best of all, takes place with the cutest animation we've seen yet this year. Yep - the Pikmin come along and carry all your data over, a piece at a time. Aww!
Above: Hey - careful with that copy of Mario vs Donkey Kong! It's a limited edition, you know
It's easy. All you need are your existing 3DS (in a usable condition), your 'target' 3DS (presumably your new one) and an internet connection. Both machines must be reasonably fully-charged, although we'd recommend plugging them both in too to make sure you don't lose any data through accidental powering down.
To start, just go to the Settings icon on your home screen, then Other Settings, then scroll right a couple of times until you find 'System Transfer'. Select this on both systems, then follow the on-screen instructions. You'll need to tap a few 'yes' boxes on each system so you can't just go away and leave it, but it basically only asks you if you're really sure you're sure you're totally sure that you definitely want to do this. After that, the magic begins and the Pikmin come to move your stuff.
Above: With a lot of downloaded games, it takes about 20 minutes to run its course
Not from the account you're moving, no. However, the memory of your original machine will be completely wiped (except for anything on the SD card), leaving it in factory settings, or 'as new'. You will also lose any data saved on the 'target' 3DS. Of course, if it's new, it won't have much on it except for some internet settings etc. About the only thing you will lose on your 3DS is your system preferences, but that's no big deal.
Everything gets moved. Any DSiWare games on your 3DS' system memory will get moved to the SD card, so you'll need to move the SD card from your old machine to your new one when you've finished. The old memory card will work exactly the same as it did, only in the new machine.
You won't lose any of your 3DS downloads and your Ambassador status will remain intact.
Above: Literally all of your games will jump over - but you'll need to manually move the game cartridge from one slot to the other. Not even the Pikmin can do that for you
Incredibly, the transfer even carries over your StreetPass data, allowing you to see how many minutes ago you met 'Spock' and which game he was last playing. All your read/unread notifications come over, all those unwatched 3D videos... Honestly, once it's done, you won't be able to tell that your new system is any different from your old one. It works perfectly.
No. For starters, the target system receives the old system's data in its entirety, leaving the old machine completely blank and unable to connect to the first 3DS' eShop data. Secondly, you can only do a transfer once every seven days. Thirdly, there are a set number of times you can carry out the transfer ever. So it really should only be done when you really need it.
But if you do ever damage your 3DS and have to go through this, rest assured the process is impossibly cute.