If I were to install a generic Wordpress template, is it possible to have a new header designed and installed in place of the generic header? If so, how difficult is it to insert the new header? Thanks.
In most instances, no it is not difficult. If your theme has an existing header, all you need to do is make your own header the same dimensions as the existing one, then save it by the same name and upload and replace the existing one.
It is easy. You need to change the image path from where it takes the header image to your image URL. Read this- http://codex.wordpress.org/Designing_Headers
Hi gooseandluba, Yes, you can create your own header and replace the header in the generic theme you are using. However, it may or may not be easy-- depending on the theme, the format of the header and otherwise. If the header is simply an image file, you can create an image of the same dimension and replace it, as gr8liverpoolfan said. However, the header may be comprised of some other code. In the best cases, the header is just a static part of the whole theme and you can change the name of your blog in WP and it'll update accordingly. Good luck!