I would take them to a jeweler or at the very least, call and ask what you might be able to do. Pearls can be ruined very easily. If you are unable to get them cleaned, you may want to have the string restrung and new pearls bought to replace the stained ones. If the pearls are small, the cost should be reasonable for the pearls. Having them restrung may, on the other hand be very expensive because of the time and labor involved.
Lew, May 2008