Tumblr Theme modification

Hi, I am looking to buy a Tumblr theme - http://ultragridtheme.tumblr.com/ and it is almost perfect except I'd like to make a few minor modifications 1. To reduce the amount of white spacing around the posts 2. To reduce the amount of grey space between the posts 3. Change the main header to a logo 4. Change the links on the left so they link to tags. That's it! Please let me know if this is something you can do relatively quickly. Thanks