Editing/Creating New Items

I'm just wondering how easy or difficult it is to create or edit some items in the game, specifically weapons, and whether I can do it without investing a large amount of effort.

For roleplay purposes, I'd prefer my Kensai/Mage to wield long swords rather than Katana, but Celestial Fury is too good to ignore, so I was wondering if I could:
1) Make a new sword that's got the same stats as Celestial Fury.
2) Edit Celestial Fury to make it a long sword.

Links/tips/guides much appreciated!