...http://elvish.cjb.net/utilities.htm - or at least, you could when I last looked there. If not, try http://telp.org/files/mm6/, but you'll have to unzip that one.And take good note of Maybeth's warning, too. Whichever character's backpack you edit the key into, make sure you open his pack and pick-up and replace every item in it as your first action after starting the game and reloading your savegame.
To tackle Gharik's Forge successfully, a magic-heavy party needs to be level about 35. A might-heavy party can do it a lot earlier.
