How can I change the way price set information is presented on a contribution page?
You can do most/all of that with an extra CSS file.  Go to Administer &gt; System Settings &gt; Resource URL's and enter a value for the Custom CSS URL.

In that file, you can add CSS to change the default appearance.  To figure out what to put there, you'll need to examine the page and experiment with Firefox/Firebug or similar.  There are lots of CSS tutorials around, but if you post a URL of the current version someone might suggest some CSS for you.