Keystone does not publish or provide model specific owners' manuals so you won't find one that applies only to your Sprinter. Instead, Keystone provides a generic, one size fits all type manual that covers every model.
If you go to the Keystone website (
www.keystonerv.com) they do have a link (Customer Service) that will take you to their Owner's Manual page but I don't believe they have any that go back as far as 2004. I'd download the year that you can find that is closest to 2004 which may be 2009. Try giving them a call to see what, if anything, they can do for you.
Remember, all of the manuals are generic and many have found them to be lacking in detail and information.
There were manuals for the various appliances and some other items that came with the unit but may have disappeared with the change(s) in ownership.