There should be no risk of an unrecoverable brick due to following this guide. However, everyone should get into the habit of making NAND backups regularly in case anything ever goes wrong. I take no responsibility for any damages that occur to your 3DS and/or copy of Smash due to following this guide.
NOTE: Everything is possible using Windows. Mac would be somewhat different, but probably possible using wine.
ANOTHER NOTE:...
Smash3DS - Updated ROM Hacking Guide
NOTE: Everything is possible using Windows. Mac would be somewhat different, but probably possible using wine.
ANOTHER NOTE:...
Smash3DS - Updated ROM Hacking Guide