You are awesome for doing this (yifan_lu, too of course)!
Does this update method also include the web browser? Either way, I'm going to attempt this tonight. Hopefully the N3DS Japanese recovery mode dialogs don't trip me up too badly. Thanks guys!
It does include the web browser. Let me know if it works if you try using my files, I set the DeviceId to 'xxx' in them since someone above said that had worked. If it doesn't then I can change it to reflect the DeviceId of the request. When I updated mine I had the DeviceId set to my DeviceId.