A number of people have gotten the file upload to work for adding files. I think there is some code and fixes posted. I don't specifically remember anyone talking about modifications, but recently some questions on changing the file uploaded were asked (and I don't remember the answers).
http://www.postcards.com
FAQ: http://www.postcards.com/FAQ/LinkSQL/
http://www.postcards.com
FAQ: http://www.postcards.com/FAQ/LinkSQL/