there r only 2 dangerous things u can do to ur wii... which is installing a new system menu or system menu IOS. (these are safe to install, but if they fail, freeze or lose power in the middle, u could be bricked)
installing a cios is safe.
if u have priiloader and bootmii as IOS, u can recover from anything as long is it isn't a corrupted system menu or system menu IOS