In a nutshell, if you want to revert to stock ICS the easiest way that I know of is to flash a stock ICS ROM using PC Odin. There is no need to be rooted in order to do that and the phone should be perfectly "stock" afterwards. Instructions may be found in this thread....
http://forum.xda-developers.com/showthread.php?t=1424997
Most of what you need to know is contained in the first post, or by following links included within the first post. It isn't difficult to do, but you do need to make sure you understand what you are doing and any risks/pitfalls before you start pushing buttons. Few things in life are 100% risk free, but if you know what you're doing it's about as close as you can get.
The big word of caution is regarding wiping/resetting the phone once you are on the stock ICS ROM. There is a risk (not a certainty) that you might brick your phone if you wipe it (including factory reset) whilst on a stock ICS ROM. This can be avoided by not wiping whilst in ICS, or by flashing a "safe" kernel that has the brick bug removed. The instructions in that thread do cover the topic. If you are already on JB then you can do your wiping within JB before you flash the stock ICS ROM.
You also need to understand that stock ROMs are regionalised, and there have been a few releases over the months for each region. Therefore it is important that you pick the correct stock ROM for your phone in order to flash it. For example, you probably wouldn't want to flash an Indian ROM onto a UK phone, or a Vodafone ROM onto an unlocked, SIM free phone. My phone was supplied from amazon.de and is a "German" phone so up until recently I have only ever used Samsung's German ROMs on it. They have English language, so really not much of a problem, but if I wanted to revert to stock ICS I'd need to vist the ninth post in that thread to locate and download this ROM....
<snip>
Sept12
N7000JPLR8---4.0.4/12.09.03-N7000OJPLR8---Download---Tunisia
N7000JPLR8---4.0.4/12.09.03-N7000OJPLR8---Download---Pakistan
N7000JPLR8---4.0.4/12.09.03-N7000OJPLR8---Download---Libya
N7000XXLRL---4.0.4/12.09.03-N7000HUILP5---Download---Italy (H3G)
N7000XXLRT---4.0.4/12.09.07-N7000DBTLRT---Download---Germany
<snip>
As you can see within post #9, there is a very, very long list of ROM possibilities. You will need to select the right one for your phone.
If all that sounds too daunting then you may be better off having Samsung take care of things for you, or perhaps a more knowledgeable friend.
FWIW I'm now running Paranoid Android on my Note. I didn't find much of unique value to interest me in Samsung's JB ROM and, using pretty much none of Samsung's own apps, I decided to try a more bloat free experience instead. So far things are looking good and I think I'll stick with PA for a while, if not permanently, as I rather like its streamlined operation and nifty phablet interface.
