Trying to match width of content+primary sidebar to primary menu width

I'm sure this will be an edit of one of the dozens of css files but I can't figure out which one, have tried several but to no affect. site=www.directpay-test.com, click System or Solution link on primary menu for static page. I want to match the width of the content being viewed by the above link plus the primary sidebar on the right to the width of the primary menu above so it looks like a single uniform box. Then I want to extend the primary sidebar height so that the bottom is the same length as the content when viewing the home page. Don't have to do it for me, just give me the file to edit and which part and I'll mess around with it until I get it. Thanks!