Ah, it's ok. Don't feel bad, everyone has to learn somewhere
So I will show a step by step then, hopefully this can help you or anyone new, and you can just ignore what you figured out on your own lol.
Changing the names of stuff is the easiest thing to hex edit by far.
1.) Like I said, copy the scenario.s11 file and save it as backup, also can make a new folder for it somewhere you can actually edit it, so you don't have to deal with administrator errors by editing the main file.
2.) In HxD, click your mouse on the right hand side somewhere, like on the KOEI%San letters or anywhere on the right, then click on Search, then Find and type "Prime" then click OK. That should bring you to the Prime Minister rank.
3.) Highlight and copy all the way down the ranks until you get to where Flying General is. Then click File/New and paste the ranks into the new file, then where it says 16 near the top, change that to 33 and it should look like this:
That will help you see everything evenly and can just go down the list and what to change.
4.) Again on the right, click on Prime Minister, and type in the name you want for the rank, I will use the "Warden of the North" example you listed, then when done, click on the last letter of the name on the left side and make sure the next number after that is 00, and it should look like this:
5.) The stats and bonus are under the numbers 1D and 1E in the example, change those and whatever other names you want.
6.) Copy that and paste back into the scenario.s11 file and put it in the Rotk folder if you moved it, and test it out and it should work. Note that some of my numbers will be different because I edited them already.