Mike,
Why not select a theme that has the basic layout you want & is something that you like the look of visually. Then create a child theme (http://codex.wordpress.org/Child_Themes) based on it.
When you say
a banner image which will be a slideshow of images
I am assuming you mean something like jQuery Cycle (http://jquery.malsup.com/cycle/). If that is the case as getting jQuery to work in WordPress is far from impossible but can be tricky I would go for a theme that already has that in it, and then just extend it to have the static top header picture you are looking for.
HTML & CSS wouldn’t be overly difficult, just copy the style.css file and the header.php file from the original theme into a new folder within /wp-content/themes/ and you’ll be set.
thanks for replying.. when i said “a banner image which will be a slideshow of images” i meant a banner image such as the one in the twenty eleven theme, but where you can upload several images and they will be displayed in a slideshow, fading from one to the next. above that image, rather than only being able to change the header text, i want to be able to upload an image which will have my website’s name. i haven’t tried child themes yet. afraid to mess around with code until i’ve read more about it
