Get stock firmware for country/carrier from Samfirmware (not 4.0.4 if you intend to root your phone in the future), flash with Odin in download mode. How ? Thread stickied near top of Q&A titled 'Flash stock firmware' has instructions. Problems with Odin flash ? Hopper8's 'Odin troubleshooting' thread stickied in General section has all the info you need to get a successful Odin flash & a 'clean slate'.
As to how instructions on another site will/won't work, no idea & won't be looking at those.. Not interested in what's on other sites given most of the info found on them has probably been posted here in the first instance anyway. You don't need other sites when you have a resource like this one at your disposal.
Once you're back at stock, you can then re-root your phone & flash whatever custom rom/kernel you want again (maybe not do that until you're totally comfortable with whatever process you need to use first).
Last edited by MistahBungle; 10th March 2014 at 10:04 AM.