Might be a little tricky using the old material. For one thing, it is not as forgiving as a new material will be. Remember, it's 13 years old ! I remember repairing a cloth seat one time, got it all back together, and then it split because the material was old.
Someone here will have an answer... Good luck, and I want to see how you do it. Mine is fine too, just sagging in the corners...