Daily Theme Header - How to Increase Advert size ?

Hi guys,

Is there an easy way to change the current banner (468x60px) advertising space to a leaderboard (728x90px) within the daily theme header? Just looking to increase the size of the advert currently to support a leaderboard.

I'm assuming the logo will need to shrink also. Which is fine. Just looking for the best way to do this.

Thanks!
Jarrah