Michael,

The "Headquarters House" is now a museum in Fayetteville. It is owned and preserved by the Washington County Historical Society.

Here is a link to their site, which also has some photographs of the structure:

http://www.washcohistoricalsociety.org/hispro/hqh.php

The walking tour of downtown Fayetteville also includes some additional Civil War related sites. I'm sure if you email the folks at the historical society, they can help you.

Best,
Dale