Well, it's 100% ok to modify the mods. In fact, that's a great idea! However, you SHOULD make a copy of the mod for the changes, and don't ever complain about something not working right unless it is a completely unmodified mod.
I should mention I am only 15, and could do modeling at the age of 14, as well as web design and basic programming, so don't ever say 'Oh I'm too young for that'. Trust me, every thing is possible if you set your mind to it. I would recommend glest.110mb.com for learning modeling/xmls/texturing/blender/etc.
If the archmage's EP is unaturally high... then just change it in the XML!
@ElimiNator: No I'm not, since I prefer to work on my own, but I did make some models for DM before, and if I had the spare time, I could help (but I don't, so oh well
). Why do you ask? Did something happen while I was away?