If you have some inkling of double gun culture it is OK to have it but the costs of a proper rebuild may not be worth it to you. Especially since 16 ga. ammo is rather costly at the moment. Even components cost more. I have a few sixteens in my accumulation or of a friend's but have shot none of them.
If you have a smith examine it it will cost you money which might indicate which way to go. You may care to just sell it and get a cheapo rotgut no-goodnick Baikal (Remington) for almost nothing. I bought three just to have something in two gauges to beat and chop on. I will try to have one set up as a semi-custom gun with light enmgraving and other work.
Look at Auction Arms, GunsAmerica, or Gunbroker to see what prices are. Do hit the dedicated doublegun sites of which there are at least two or three.