Good news! Your template (cherry zen) significantly modifies the standard page organization, and while that would usually not be a good thing for further customization, this template is set up for easy CSS manipulation.
There will be a number of things you will have to change, starting with a main background image, but you can get a taste of the possibilities with a quick paste into your stylesheet.
Find this:
Code:
.leftBoxContainer, .rightBoxContainer {
margin: 0em;
border: 1px solid #CECECE;
border-bottom: 5px solid #CECECE;
margin-top: 1.5em;
}
and after it add this:
Code:
.rightBoxContainer {
margin: 0; width: 30% !important; float: left;}
#navColumnTwo {clear: both; width: 100% !important;}
#navColumnTwoWrapper {width: 100% !important;}
For the actual edits, you will want to find the original rules and edit them, and make some settings in admin for Column Right width and Column Right Boxes width.
These changes will apply to every page on your site, unless you add rules to specify otherwise.