yeah my brother got it me from amazon , this one
http://www.amazon.co.uk/s/?ie=UTF8&k...l_8ofnrsi18r_b
yes , you can use the left mouse button to shoot thats what i use
, the software which you download lets you remap most buttons , I swapped L1 for right mouse button (R2 i think) , i now use grenades on the 'nun chuck' and aim and shoot on the mouse which also has buttons by your thumb for re-load , mele , swap weapon which you soon get used to .
setting the sensitivity takes a while to get it to your playing style , i have sensitivity on 'insane' in game and on the nunchuck (which can be set throughout game) i have it set between 3-4 , there is also a frag button which is apparantly good for sniping but haven't used it at all yet .