I finally figured out how best to change my header images from the default ones. I found some good instructions, made a child theme from WP Twenty Eleven and then installed the Cimy image rotator plugin, upload all my new images and updated some code:
The tricky part was figuring out how to eliminate the extra spacing that the plugin code added when I replaced some php code in my headers.php file. I had to find the margin value and change it to 0 auto; Figured this out thanks to JennC on this helpful forum post.