Removing image banner from post.php

I changed themes but the image banner under the menu didn’t get removed with the new theme. I was able to remove the image but the banner is left and gray in the post.php file and I can’t seem to get rid of it. What I really want is for it to look like the Grocery Store theme but I don’t know how to completely replace everything without starting over, which I can’t do, so if it can’t be removed completely, I would be satisfied with having the gray area be about a quarter inch above and below the page name instead. Any assistance would be appreciated.

The page I need help with: [log in to see the link]