A Guide is out of the question from me at the moment but I'll give you some pointers. The Magic images are stored in Magic/MagicEx and so forth. Using kaori Wil Editor, you can export all the images into a directory and then you cna do a few things...
1. Change the images by hand using a Paint Program
2. Use other spells (newer ones) in there place by moving and renaming the images.
You would then finally rebuilt the WIL file and now would see the new look.