Alot of these questions youre asking have been answered a million times before (just read) but Ill answer them
"Thanks guys for the replies. When I softmodded the wii I did a nand backup. Is this some thing that should be backed up monthly ? does it ever change ?"
Well, once you have a backup you dont need to back it up monthly unless youre always adding/installing new wads and other things on a regular basis. My wii is at a point now where its set and I dont have to do much else but the occasional update of a ios once in a while. I havent done a backup in months and havent done so since my wii is set (so Im gonna do that asap) Lucky for me I have boot2 so I can experiment alot. I assume you have bootmii as IOS make all the backups you want but be very careful restoring your nand using it on IOS. I would recommend plugging your wii into a battery backup before restoring using bootmii IOS (just to be safe) hopefully youll never have to take it that far.
"Can you recomend a good tut for installing priiloader, PS does it change much from reading it sounds like it sort of inserts its self before the wii menu ? do you need a special controller to use it ?"
As for priiloader, Its an easy install. A tutorial isnt needed, however if you want a tutorial you can find here:
The Complete Softmod Guide (the best compilation of info around imho)
http://sites.google.com/site/completesg/
Just be sure to download the latest hacks.ini from wiibrew run the dol from HBC to install and youre done. Enable/disable the essential hacks and thats it. No need for special controllers as you can use the wiimote to access the options, however if you enable a recovery option (i forgot what it was called) youll need to use a gamecube pad to activate it. Well just read man, and youll find your answers.