I would suggest contacting places that handle this sort of thing regularly. The Smithsonian, Metropolitan Museum of Art, Tower of London, the Vatican, Musee` d'Armee, and the Louvre are such places that come to mind. Try to get guidance from their head curators. They get their advice from real scientists and professionals as to what is the BEST way to do it, not just the most practical. Taking advice from places like an Internet forum is very risky. They may suggest a UV protected low light and oxygen-free display. Practical? No. Inexpensive? No. But it MAY be the BEST. It'll be up to you to decide on the economies of it. In any event, at a minimum it won't hurt to wear gloves when you handle it.
As far as any restoration goes, you may even wish to see if you can contract with those places (such as above) to do any work you wish to have done. I personally wouldn't trust myself to do it properly with a hobbiest's knowledge and resources. You may indeed have a gun that is a $100,000-$200,000 gun, and priceless as to its' historical significance. If you treat it that way you'll be in the right frame of mind when you handle it.
