I agree with
Mr. Guzman, what you need is a VERY good custom broker. That and a truckload of patience.
A lawyer will not be of help in the actual process of customs clearance. I will take the liberty of adding a few tips of my own:
Get a good customs broker BEFORE you even plan a first shipment. Meet him, talk to him, go over it a zillion times and make sure you understand everything. Before you ship the jewelry make sure that your broker has received the documentation before hand.
If you ship your merchandise via a carrier (as opposed to bringing it with you as part of your luggage) you MUST insure it. The insurance is very expensive (for jewelry), but worth every penny. I would assume that you will use an air carrier. Make sure you know when your plane arrives, and have your customs broker waiting for it there. Forget about safe storage in the airport.
If you bring it with you, bring it in a hand-carry, do not put it in your regular suitcase. Again, have your customs broker meet you at the airport.
Check
this other post about a similar subject. If you need more info just shoot away. I will torture one of the Customs Broker in my company and will tell you.