But as I dont have a huge knowledge on CSS I am not sure what the command could be to move the X to the top. I can see the line float: right; positions it to the right just not sure who to get this to the top.
To move it directly to the top, the title bar, you'd need to do that in the skin.js file. The skin.js file is what creates the HTML markup for Shadowbox. If you only want to move the close button to the top, you could relocate #shadowbox_nav_close and nest it in #shadowbox_title, then rework skin.css to pretty it up.