Where did he live? Is he still alive? If not what did he die from? Where was it, that he had the infamos, running mountain in his back yard?

Walter Payton, a/k/a Sweetness was from Columbia Mississippi and played for the Chicago Bears.

He passed away on November 1, 1999 from a rare liver disease known as primary sclerosing cholangitis.

Sorry, but I don't know about the "running mountain"

Here is a link for more info on him. Try a quick Google search on Walter Payton.