Add Google Search to Search box?

I like having the search box in the header area. However I'm stumped as to how to change the box (add code) to change it to a Google Search box. I want to add this to my array of AdSense components and have the code but can't figure out where to insert and how to make it stick. Am I wasting my time. Is my only option to add a box to a sidebar via widget?

Thanks,
Laura
www.milehighonthecheap