In Seattle for decades (my Dad had a custom wedding ring made there in 1967), Monroe & Crane specializes in custom and estate jewelry. My Mom recently inherited several pieces of jewelry, and has loved working with them to reset a few and refurbish others. They have also worked closely with her to design new pieces that make use of the great stones, but fit her own style.
The service and quality is top notch, and I imagine the price goes with that. But if it's a special piece, it's certainly worth talking with them and getting a estimate. They're located downtown on Pine St., across from Nordstrom, and are open Tuesday - Saturday.