Your saved games are stored in ...\Crusader Kings\scenarios\save games\. The file names should be the same name as that of your save game and have an extension of .eug, and as you found out, you can edit them directly with a text editor of some kind, be it wordpad or notepad or whatever. Reading the scenario file and the associated values can be tricky or take some understanding of what you are looking at or looking for or wish to change before you can make any valid change without messing something up, but you can reason it out.
Alternately, there is a program someone wrote that you can get that will allow you to change the same data, but in a more meaningful and easier to understand way with an interface called CrusaderEd.exe. (Crusader Edit)
Unfortunately, the program is a bit of a pain to find now on the web, so if anyone has a working link to a download, feel free to post it.