[SOLVED] Possible to set layout container padding for left & right to different value

First of all....LOVE this theme - "theme" doesn't do it justice compared to the other stuff out there. I'm definitely going to send some love via Paypal....

Hopefully this is an easy answer but I haven't been able to find it asked anywhere yet...I'm trying to make a site where the content (header, nav and page content) is off center from the background image. So I need a left container padding of 310px and a right of 140px (with the page content being 574px, I'm designing for 1024).

I figured out how to put in one value that affects both sides under "Overall Styling & Config-style LAYOUT". I tried putting in "padding-left: 300px; padding right: 140px;" - but it just pulls the last number value and renders that. If this is something I can set in the code, what file is this located in?

I'm not a programming expert but can understand some php so I'm not afraid to go in there, just have no idea where to look. I'm using Atahualpa 3.4.1. Thank you!