Customizing a theme

I have some questions about customizing a theme. I am working with the “Pretty In Pink” theme from WPDiva. I have it running here:

http://testing.00goddess.net/wordpress/

I would like to tweak this theme a little to get it looking the way I need it to look. Specifically, I want to replace the top bar, which currently has the title, with a typical top navigation bar, so it can be used to navigate around the pages. Also, I want to replace the “tagline” which is now in the upper right with an image… I was going to make it a gif with a transparent background so it can float over the header/background image. Can anyone give me some suggestions?