I browsed the web for a solution all night and got as far as changing the background image files and using an adjusted Default theme which adds an extra sidebar/column next to the right one. (see here)
I've been editing style.css, adding the extra bits where needed, simply copy/paste from the 3 column Default style.css.
And yes, I also adjusted the functions.php and index.php files, added a sidebar2.php, the 2nd sidebar also shows up in the widgets section and I added a few widgets because from what I've understood if you don't add widgets to the new sidebar, it won't show anyway.
After all the hard work.. still no 2nd sidebar and an insanely messed up 1st sidebar. Where did I go wrong???
My head is exploding, I could really use some help right now. :(