I activated a new theme, but…

Oops…I may have committed a No No!
I’m relatively new to all this, just having finished my first website in late August!
I was working with the dashboard and I clicked on ‘Appearance’ then ‘themes’ and was directed to a selection of new themes. I scrolled through some of them and then previewed ‘Atahualpa’. When I saw my website in this new theme, I liked it and then, Voila, I clicked ‘activate’ and the new theme became my website. I kind of like this theme and like it better that 2011 which was my original theme.

Here’s the problem…I want to change my header images to my custom image, but there’s no easy edit like on 2011. Atahualpa use code a lot instead. Also, there’s no Edit button when in login mode on the pages. Also, I see that some of my rss feeds don’t open in a new window as I prefer, but leave my site.
Is there an easy way to do all this editing, without having to learn code? Or should I revert to 2011 theme?

Can someone shed some light? Thank you!