Technically, stainless isn't a finish. It's a kind of steel. If it was a Bright Stainless model then sending it back to Colt would result in them polishing out the scratches and bringing it back to a Bright shine. There will be no "refinishing" so to speak on a stainless gun. To a Python purist, there might be some loss of value, but since you don't have the box or paperwork on anything anyway, it doesn't have much of a collector value anyway.
If I were your friend, I would shoot it the way it is. But if I were going to send it back to Colt to be repolished (and I've done this to one of my Pythons) I would just plan on keeping the gun as a family heirloom and forget about the "value". Not having the box and paperwork will hurt the collector value of the gun more than whether or not was sent back to Colt for a polishing.