I would say for most people, though, that it is not simple. You will probablly be able to find your name in the file and edit it, but when you load the game it will most likely revert back to a previous saved state. I mean that it will count your edited save-game as invalid, but it may be able to use a backup version.
Youre right. Even when I change one single letter in a new game it doesnt work. Hm.