A couple years back I soft modded my virgin 4.2u LU30 Wii with using the guide by [Ninja]UK from 17th Oct. 2009 and to play Skyward Sword and USB backups. I also installed a couple of custom snes wads and that was it. It has just been sitting around for a while so today I thought I would get back into soft modding and update whatever it is I need updated to play my Gamecube backups. I've been out of the game a while so links to any up-to-date guides would be appreciated. Here's some info about my Wii:
Bootmii v1.4 (Installed as boot2)
WAD manager 1.8
Configurable USB launcher v70
Neogamma R9 Beta 26
The softmod Any Wii guide is what we recommend everyone start with. That guide is linked in my signature.
As for getting gamecube backups to run, I'm not sure if neogamma will do that along with Wii games, but we recommend USB loading. See the FAT32 and Dios Mios guides which are also linked in my signature for more information about those.