This guide has now been updated to cover ALL wiis, 3.0-4.1 any region, and all LU64+ and foreign equivalents. (dunno about those Korean ones?)
LU64-65++ serial no. wiis still cannot downgrade their firmware - if you bought your wii this year then it most likely will be one, so don't downgrade it!
Make sure you do the steps in the right order or you could run into problems, and read the guide through a couple of times before trying it. Read ALL OF IT! First person to asks if it will work on their wii gets an infraction!