Hi Sean, You can call me Sister.
If you're working in WP, you should be able to change or delete the title from the 'options' page. Looks as if it's a tagline, which should be handled from the 'options' page as well. If not, then you'll have to use the theme editor to look for it in the 'header' code and delete it.
To change your entire header image, ftp your new image up to the images folder in your theme, then go into the theme editor (under presentation), pull up the stylesheet and scroll down until you see something like:
#header {
height:191px;
background:url(img/
blankheader6.png);
}
Change the part in bold to name the new image. This will change the
entire top header image of your blog, so make sure the size is the same. Aside from creating a whole new header image with your image in the corner, I couldn't say how to put another image over just that part of it.
Hope this helps some.