only thing i can think of to do is to set yourself a nickname on your profile page, at the bottom left where it says "misc". once the game's started, all the manager's profile details (name, nationality, fav club etc) are set in, they cant be changed. only other way is to resign and add a new manager...
^ Correct. Just set yourself a nickname, and all instances of your name appearing will be replaced by the nickname.
The only downside is that the full nickname will always display. So if your name is Robert Jonzowski, and you set your nickname as Bob Jones, then all news articles that used to say "Jonzowski wins Manager of the Year" will read "Bob Jones wins Manager of the Year". Your new surname by itself will never display anywhere.