I was thinking of doing the same thing so a friend told me about 1-800-gold-kit.
You call the phone # and an automated voicemail box takes your name and address and sends you the info to send in your jewlery. I think I am going to try it with my broken pieces and see what I get before I do anything with the wedding ring. They send you a check in the mail and if you dont like what they have given you then you return the check and get your stuff back.
I have not tried this yet but it may be something to try. It wouldnt hurt to go to a jewlery store too...and see what they say. You dont have to sell it to them...just get an estimate.
Good luck.