Change Nav Bar from Vertical to Top

I need to change the nav bar on my site from left to top. Of course, now every page’s design/layout needs adjustment because now that the left nav bar is at top, none of my banner images span the full width of the page and the rest of the layout is off center.

Is there an easy way to get every thing centered and full width?

I’ve tried to resize the banner images, but it’s not filling in the area where the nav bar was. It’s pushing the image to the right and then I am not able to drop it to the left. The same with the all the other sections. I can’t drag them or reposition them to the left.

Any ideas?