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To answer your questions, yes, all of that is possible. To perform the edit, you'll need to first get the excellent KOTOR Tools. Using that, you can edit the spells.2da file to change the alignment/cost of Force powers. Look under the forcepoints and goodevil columns. If you want to change the descriptions as well to match the changes (not needed unless you want the descriptions to be correct), you'll need to use the TLKEditor. Edit the entries inside the dialog.tlk file by looking up the numbers provided in the spelldesc column of the spells.2da file.
As for making the mod usable on the XBox, I'm not sure, as I believe you need to mod the console itself to make it accept custom mods.
- Star Admiral