The method to install the Homebrew channel described in this article is an old method. The new way to do it doesn't require the Twilight Princess game.. check out this great site for the most up to date way to trick out your Wii:

http://www.wiilovemario.com/The-most-up-to-date-Wii-Homebrew-and-Backup-...

And firmware version doesn't matter anymore.. it seems like you can install the Homebrew channel with any version Wii. Have fun!