Do I need to obtain some sort of release or agreement,
before I put these photographs up for sale online.
How could I best sell them in general;
by selling them online myself or by finding a stock photo dealer to work with me to sell them for profit. Looking for advice. Thanks.

"Do I need to obtain some sort of release or agreement,
before I put these photographs up for sale online."
NO you don't this subject was hit upon on Photoshop user TV week of January 26, by attorney Ed Greenberg.

http://www.photoshopusertv.com/?p=299