Well, if you have to free some blocks, all you have to do is delete some of the WADs you installed to make room, then reinstall them when you want them back.
You shouldn't format your system memory unless you absolutely need to. That is, screw up your Wii or something. If you format, everything (everything!) will be erased, leaving you with a completely empty Wii, as if it was new.
my old MX518 also had the rubbery coating starting to come off, i can never get it back to un-sticky state, the harder i clean it the worse it seems to get, same thing with the wrist rest on my old keyboard too