[Theme Padhang] Header size….

Does anyone know if it’s possible in any way to make the header any bigger? I’m trying to make my logo fill most of the area however it is tiny in comparison.
The image I have created is 1000px wide yet when it loads onto the page it is resized down. You can see it here: http://www.markgriffithsmusic.co.uk

Any help would be greatly appreciated.

One other thing – Is there anyway I can make the large white boxes where the information goes slightly transparent?

Thanks,
Mark