Two ways to look at it.Agree with the above in regard to maybe best to sell this as it is then, if you are not wanting to play it. Someone will love this horn and invest to keep it. But I am less sure you would get the money back necessarily if you did get it set up.
Be careful polishing gold plate - it is soft and thin, and may be abraded or worn by harsh polishing.I second. If you intend to play, be prepared for several hundred bucks to get it playing, then you'll have a great horn on your hands. Otherwise, sell as-is - almost. I'd spend a couple of hours polishing/cleaning it up. That could net you a couple hundred more bucks.