Is there a jeweler in your area who sells antique jewelry? That is probably the best choice. If you don't know of a reputable one, I'd go to a regular jeweler and ask for a recommendation. I know a guy in Waterloo, Iowa, but I'm sure that would be loads of help to you
I'm going to be going through the same thing relatively soon with my wedding ring. I also don't know what protocol is for getting rid of no longer needed wedding rings. I guess I'll figure it out!
Remind me the superstition with opal rings?