I have a photography buddy who owns this lens. He is a Nikon shooter from way back, and this is the first telephoto he ever bought. It is almost unused, and appears to be in pristine condition. He bought a Nikon 80-400 zoom shortly thereafter and just didn't pick up the Sigma any more. He knows I am just getting into photography, and wasn't sure if it was possible to convert, but said if I could do it, he would sell me the lens for $200-300. He still has the receipts, and it cost him $850 when he bought it.
Is there such a thing as a Nikon to Canon lens mount converter?