-What files dose this mod edit and how dose it work?
I had to change two files, the "DefaultPlayerSpell" and an NPC called "player". with the default healing spell I renamed it "No Spell Equipped" and changed it's cast value to 999999 or something, that way you cannot cast the default healing spell or after you use a scroll it defaults back to "No Spell Equipped". I also removed "flare" from the "player" NPC, so now you don't start with that ether. This might be a slightly clunky way to do it but it was the only way I could work out how... and there are no other mods I know of that do this and actually work.
-Possible problems
I don't think you can buy "heal minor wounds" in game. It is in the files but it has not been added to any NPC's who sell spells, as the "DefaulPlayerSpell" heal is not the same spell as "heal minor wounds". I have not added it as I want to avoid incompatibility. You can still buy heal major wounds.