Need styling help for ad between posts

Hi all,

I run a self-hosted Wordpress blog called materialicious, and recently I joined the Glam Media Ad Network. Even though I write what is considered a well-regarded blog, it doesn't earn me squat. I've run AdSense since the beginning, but really needed to kick things into high gear, since traffic is rather high and I deserve to get paid for my efforts!
Glam provides the code for the ads (3 ads only) and that's it - no help on positioning, styling, nothing. It's ridiculous.
Recently I ran across Ahmed Bilal's post, How to Show Ads between Posts on your Blog, and I used his instructions for placing the one ad, and it worked, of course. My problem here is I need to quickly figure out how to properly style the 300x250 ad in that space so that it is dead center (like on Apartment Therapy). The other thing I wanted to do was add a leaderboard above the header, properly padded all around (10px?), and centered.
Truth be told, I'm not really wired to do this sort of work. I can figure it out eventually, but I just don't have the time, nor do I have the money (yet!) to pay someone to do all the necessary design work.
Can someone help me out? Either by posting some suggestions, or by pointing me to appropriate sites and/or forums?
Much obliged in advance,
Justin