Change main column wdith in theme 'Fancier'

Hi i just found a theme that matches 80% of my needs, i just need to extra things :
1- change main column width and set it to 640
2- clear title and replace it by an image header

Can someone explain to me where to go, what to do, what code to type (i’m new to wordpress), or maybe show me plugins that features those options.

Thanks guys.