Change size of content area and sidebar

Hi all- Trying to edit my theme, I have some CSS knowledge, but I’m a little over my head.

Here’s an example page. http://carissalyn.com/project-365-day-238/ I want to align the sidebar to the right, then expand the content section to be wider.

I believe the relevant css to the sidebar is in screen.css, here: http://pastebin.com/sywcjXE6

Here’s the sidebar.php class: http://pastebin.com/YBhEh91P

And here is index.php: http://pastebin.com/zL1LhJ7c

I was able to re-size the sidebar in screen.css with span-8, I tried adding a right float there, which didn’t work. Any help is greatly appreciated!