OK two quick questions

How can I make my Wii a Virgin system again after softmodding 4.2? This is mainly for future knowledge. Before I updated I did back up the NAND etc. Is it just a case of placing this back on the SD and then Boot Mii shoudl run it? Am I right in presuming this?

Also do I just use Wad Manager to install Wads on a 4.2 system?