Jordy, how 'bout trying another template completely. You can download one from here...
http://themes.wordpress.net/
This might be easier than trying to change the blue banner.
Once you learn the basics of FTP you can upload the new template to your site and when you login to your WordPress Admin area, you will see the theme as an option. Then you can select the new theme and WordPress instantly switches to the new look.
Of course if you want to change the images then that requires you to know how to FTP. But I do recommend you take some time to learn how to use FileZilla. If you want to customize your template images, it's good to know how to use an FTP program.
This site has a great tutorial with pictures
http://www.velnetsupport.co.uk/parrots/FTP/Filezilla/
1) So first step is to setup an FTP username and password with your host.
2) Follow the instructions in that link above to connect to your host with FileZilla
3) Find a template you want use
http://themes.wordpress.net/ and download it.
4) Now using FileZilla, upload the entire new template files to the themes folder of your blog (The themes folder of your blog is located inside the folder where your blog sits) So for example, my blog sits in a folder called "blog". So when I navigate to that folder the path is /blog/wp-content/themes
When you upload the entire theme you downloaded into this folder then it will now appear as an option under "Themes" in WordPress
I agree. The more you want to customize the more you'll have to learn about the coding but trial and error is really the best way to start figuring things out.
But your first step is to definitely become comfortable with FTP. It's not too complicated. Basically it's a program that lets you see a list of your web server's files and folders.