You could look at
coder62's Itemtype decrypter/encryper>

Makes it a text file, then use any text editor to open it up.
ItemType editor already made
at10ti0n Itemtype.dat editor v2 -beta>

When using the batch function it doesn't edit the sheilds. You must go back in to edit those by hand, using coder62's De/En and text editor. Decompile this and see how it works.