I have been using WordPress for around three years now. Unfortunately, I ran into an issue and had to reinstall WP. In my previous installation, a friend of mine had modified some code for me to widen the content area of the theme I was using, however, I do not want to ask him again how to do it, and I just want to learn this myself.
If anybody could give me a bit of help, I am using the Twenty Twelve theme, here is a link to the site: http://www.jacobwcrosby.com
All I really want to change is the giant gray bars on either side of the content to be gone, or at the very least, much, much thinner. I always use photographs that are about 900px wide, and I am not able to do that now... I dislike people having to click a link to view a large image, it works better this way to keep them on the site.
I am also very open to a new theme that would allow for a 'blog' style with large images, none of the gallery junk, I really dislike galleries.