There are.
I've run accross mods that add different monsters and skill sets...but never tried any.
But it sounds like you're talking about a plain editor. There's one called the Hero editor, or something like that, that will let you change classes, levels, skill points, equipment, Act, etc. Run a search and avoid sites that are somehow looking for money for characters and other silliness.
However, I can almost guarantee if your friend uses it it s/he will tire of the game very quickly. The game's merit lies in the progression, the fight to stave off ineffectiveness against increasing challenges.
With a changed character, you'll find yourself bored with normal progression. After you've beaten the game, progression is essentially all there is. When that happens, you'll delete it and sell the cd like I did lol.
