If I sell something on Craig's list, do I have to allow for a refund if requested?

Not sure if that makes sense. I'm selling an expensive piece of jewelry on Craig's List. I have a buyer. The jewelry is genuine. My fear is what if the person buys it, replaces the diamonds w/ fakes and then wants to return it for a refund? I'm the type of person that won't even take jewelry to a shop that doesn't have an onsite jeweler for fear they will swith my diamonds. Am I being paranoid? Once I get the money, I want to pay off some bills not hold on to it just incase they have buyers remorse. What do you think?