pearlyblack,
The problem with selling our used jewelry is that it's....well, used.
Even if it's in great shape, there is depreciation simply because it is not new any more. Also, pearls in particular do not tend to hold value on resale the way precious metals do.
If you can find a similar item that has already been sold, it will give you an idea of what you might get for it. Otherwise, try to find a similar item for sale by a jewelry store online, and price yours at 50-60% of that and see if it sells. You can always drop the price if it is still too high.