When I say to format the sd-card, I mean to format it on the pc erasing all data. Formating is done at the begining of each of the 3 chapter. After the format the sd-card is clean and a zip file with certain apps is extracted to the sd-card. In chapter one there is the hackmii installer, in chapter 2 there is MMM with a bunch of cios wads, and in chapter 3 you have the final applications included in this guide.
When this guide is complete you will have the HBC and bootmii installed to the wii, a loadmii channel and an autobooting neogamma channel installed to the wii. You will have a forwarder installed for cfg usbloader. On the sd card you will have cfg usbloader, homebrew browser, wiimc 0.5, and savegame manager gx- you can add many many others to the sd-card.
All files you need to follow the guide are included in the download zip packs, you don't need anything extra.
Modifing your wii does have some risk, like bicking the wii permanently- this is not likely to happen. There are really only two ways you could brick, if you lost power or for what ever reason cios80 did not install properly, this could brick the wii- it is very important. Also if while installing priiloader, if the installation fails, your wii would be bricked. This guide used priiloader 0.4 which is better tested than the new 0.5 installer. So, there is risk but it is very safe, well tested method. Thousands of people have done this guide and there have not been any issues. One person failed to install 4.1 properly and bricked, another bricked installing priiloader 0.5- that is all I have heard. The isntallation of 4.1 has since been modified and I reverted to priiloader 0.4, have never heard of an issue with it. But if you mod you wii and brick it, it is not my fault, so you need to be willing to accept that risk.
You don't need to be online, possible the issue with priiloader 0.5 is related to this, but it is not in this guide.
When your done with the guide, you should have everything you need, and the ability to add whatever you like.