Originally I thought it was a huge no-no to change any of the adsense code. But if you look at sites like Fark, they change the adsense code to fit their layout. There's no way that Google hasn't noticed a site like Fark so they must be somewhat forgiving of this.
The question is, if I make it clear that it's Google's search am I allowed to change the code? Note that I only want to change the search button to a styled search button that fits my layout.