Brick Prevention- Things you should never do
2- The sd-card can be backup onto your pc and formatted. But you will still want it to run whatever homebrew apps you wish. I prefer to run my loaders from my sd-card and install forwarders to the wii.
3- Yes you can, but why would you want to. Unless you plan to make it a virgin for good, don't do it. Also, some of the techniques involved can be risky, it is best not to.