Monetize Themes

Hey guys,

I'm looking to monetize my WPMU network. I know how to add Adsense ads to all blogs. But I'm looking for something more subtle like replacing the traditional search bars on all the sites with Adsense for search (using the Google search bars instead).

Is there anyway to do this in bulk for all the sites or would I have to edit the search.php for all themes? And if that's the case, how would I go about doing that when Adsense gives me HTML code but the themes use php??

Thanks