Engagement ring 3d model

I have a design for an engagement ring that I need to have as a nurbs model in Rhino. I've already made a mesh version and tried to learn to make a nurbs version (when the jeweler I'm using needed it) but it is taking me longer than I had hoped to get to the proficiency needed so I'd like to just get it done by a professional. I have the mesh model that I made and I have a nurbs model made by my jeweler that doesn't quite reflect the model that I made as well as I would like. You could modify the existing nurbs model or start from scratch - whichever would produce the best results. Thanks!