Hi Krank, excellent guide but I ran into a few hiccups that I think would be useful for some people to know about:
1. For region-changed Wii's, you may not be able to accept the EULA if the latest version is not installed on your unit. Mine was a Korean LU64 region changed to NTSC-U (4.0). I followed all the steps but when I tried to activate WC24, I was prompted to download and accept the latest USA EULA. For this, I downloaded the USA EULA v3 from here and installed it. Only then was I able to simply click on "Agree" without having to download a the "latest" version of the document.
2. After installing the instructions here and activating WC24, the Shop Channel, Photo Channel, News Channel and Weather Channel all worked fine. The only disadvantage is that having a region-modded unit, I wasn't getting region-relevant weather and news - it would always default to the US data. Which is something I can live with, but still. :-P
3. As mentioned earlier, though, following these instructions DID break my ability to play backup discs through the Disc Channel. However, reinstalling DarkCorp v1.1 easily remedied the situation without breaking the Shop Channel modifications made. I had to install the FULL version of DarkCorp in order to ensure I got all the IOS' and files properly installed. (Please note that the linked page is in German but the downloads are all in English.)
The net result of this? Not only can you still play backup discs through the Disc Channel (sayonara, NeoGamma!), but the Shop Channel is now fully activated with the ability to download all the DLC your heart desires. On top of that, the awesome selection of VC and WiiWare available through the Shop Channel itself.
But why do I even want to enable the backup disc-loading abilities in the first place? As has been commented in many many places, isn't it supposedly better to load everything through your favorite USB Loader? Reduce the wear on your discs, etc. etc. etc... to which I say, YES it's faster and more convenient to load through the USB Loader (in my case USB Loader GX) but that comes with the distinct disadvantage of being unable to recognize and use SDHC cards. I am currently using a 16GB Sandisk SDHC card and it's got more than enough space for all the DLC and WiiWare / VC I want. But if I try to load RB3 through USB Loader GX, the card won't be usable and I have to default to a standard 2GB SD card - not very capacious by any measure. So until USB Loader GX is capable of SDHC compatibility, I'll stick with my Disc Channel for the meantime.
PS: If there are any other USB Loaders that ARE capable of recognizing and using SDHC cards, I apologize for my ignorance. I'm still very new at this and don't yet want to risk doing anything wrong by playing with Uniiloader or WiiFlow or anything else. I'm still quite happy with USBLoaderGX and will probably stick with it for the foreseeable future. Although I must admit... the NAND-emulation/Uniiloader route is very very tempting....