Yeah, Alot of fail here.
What you are proposing is a very dangerous procedure, especially for one that admits they know nothing about the modding process to begin with.
My suggestion is to ask the person who modded it, then at least it would be someone who has some familiarity with messing with the consoles operating system.
If you want to do this by yourself, you may as well go out and buy a new wii console. Because chances are this one will be useles by the time you are done.