Like bg4545 said, installing homebrew won't brick your wii, and neither will any of the apps on wiibrew will(with the exception of a few, but they are clearly marked, and as long as you don't do anything stupid with them you'll be fine). On the other hand, there are apps such as downgraders, wad installer, usb loaders and other apps not on wiibrew or the homebrew browser that are fail and may brick your wii. As a basic rule, if it's on wiibrew or the homebrew browser then you'll be safe, otherwise you may be risking your wii.