How hard could this layout be?

I'm beginning to think that a simple layout re-work'ing is just not going to happen for me without asking for help. I'm trying to get a basic layout like the one shown here (I've attached).

Can an extremely kind person help me figure out what main files I need to make these changes? I've already got the sideboxes the right size and the main layout how it needs to be. However, I do not know how to get my links to show up between my header and the main content. Is this possible? I've just gotten so overwhelmed in what should be a simple task...it's turned into such a nightmare for me. I appreciate anyone's insight. Thanks so much.

This certainly should not be difficult. A link to what you have so far would be helpful. There are a few things we need to know before we can give the best advice.

What "links" are you trying to relocate? The ez-pages? The "Home Login etc." navbar?

Much of your work will be in /includes/templates/your_template/common/tpl_header.php. Blocks of code can be moved around to rearrange elements.
What background images do you have made up so far? You will probably want one for the header and one or more for #contentMainWrapper and its components.

OK, you have the header navbar still in its usual place at the top of the header, and you have moved #navMainSearch to below the logo.
If you make ez-pages for additional content, you will be able to specify that their links will show in the header; they will appear in the vicinity of the gap in your image when you turn on the ez-pages header bar.

Make a background image for the header which has the right height to fit above the ez-pages navbar, with a transparent ground so the body background can be seen at the corners.
Make a background image for the main part of the page which has the rounded top corners, and is tall enough to fit any page height you can imagine having. A simple background image like you show will not take much more filesize for being tall.
Make another background that fits the previous one, with the bottom rounded corners if you want them. This only needs to be tall enough to fit the footer area of your page.

In your stylesheet, make #mainWrapper have no background-color or -image, and eliminate background-color from most page elements (there will be some elements where you will want it.)
Put the header bg in #headerWrapper {}, the main bg in #contentMainWrapper {}, and the bottom bg in #navSuppWrapper {} or #siteInfoLegal {}, depending on how you want it to appear. If it goes in #siteInfoLegal, you will need a slice of the main bg to put in #navSuppWrapper.

For template tutorials, look through the tutorials/FAQ section. In Template Customization/ Building Overrides you will find "How do I create a new Custom Template?" and related articles.
With several thousand files, a complete list of files you might want to modify is impractical. You will likely want to work on
/includes/templates/your_template/common/tpl_main_page.php,
/includes/templates/your_template/common/tpl_header.php,
/includes/templates/your_template/css/stylesheet.css,
/includes/languages/your_template/english.php,
/includes/languages/english/your_template/header.php,
/includes/languages/english/html_includes/your_template/define_main_page.php and others.

Check the forum - First Steps > Second step in setting up your cart - templates, and the Stylesheet subforum.

Wow, I just wanted to say thank you for your response on this. I realize it's over a year old, but thank you very very much for your response. If I remember right, I got really frustrated and ended up buying a template.

I wanted to publicly thank you for the time you gave in responding to me.