You have to downgrade so you'll be able to s-off, because with s-on you can't have perm root. I don't recommend you to use Ace Hack, i think misc_version method is pretty much safer, but remember you have to read everything (radio version!!!, hboot,....) in order to prevent any hard brick
You don't need perm root you just need temp root (using superoneclick), although
you have to change the misc_version to the Ruu software your are using to downgrade (i.e 1.32.405.6). Do md5check for all downloaded files.