So I was given what I believe to be a cz ring. It's absolutely stunning. I do not know the size, or the origin. It appears to be an 8mm round or something close to it. I need to get it resized somewhere though. I live in Tennessee, close to Nashville, and it's hard to find people that work with sims unless I send it in. Does anyone have any recommendations on who would be able to help me with this? Suggestions? And is there any way to find out what exactly I now own?

You could ask the person who gave it to you or any jeweler should be able to test it to see that it is CZ or not.