Displaying Posts in includes

I am in the concept stage of building a site for a photographer who knows nothing about code. I would like to build a basic site with a header that contains an image that the client can modify via the admin panel in the form of a post. This post would retain its ID throughout the life of the site, while being updated/edited frequently.

The main content would hold the recent post (no tricks there.)The footer would stay simple as well.

THE QUESTION IS THIS: How do I display one post in the header, another in the main content, and then even one in the footer?

Is this even the way to ask the question. Any thoughts? Thanks in advance. Take care, ~ JD