Does anyone know if there is a way to get the top logo directly in the center of the page with the Cobalt theme?

I edited "header1.html" and added the code to center the picture, but that just centers it within that cell. The problem is it splits the top portion into "header1.html" on the left and "header2.html" on the right.
In looking at the file "header.html", it looks like it has the content of header1 and header2, so it seems I should be able to use just header.html and not the other 2. If I can do this, I would be able to center the logo.
The problem is that I have no idea which file I would need to edit in order to make it show header.html instead of the other 2...

Sorry if i got confusing! I would appreciate any help anyone could provide!

http://www.venturelandgames.com