Search for clues as to the current disposition of Talvash's necklace within Uldaman. The slain paladin he mentioned was the person who has it last.
A competitor of mine started a rumor that my necklace cursed the paladin. Needless to say, no one wants to buy cursed items from a jeweler.
[player], I'll make you a deal - find the gems and I'll reassemble the necklace, so long as you'll advertise that I do NOT make cursed items!
Try looking for clues in Uldaman; maybe see if the paladin's body is down there, since he's the one who we know had it last! When you find the gems you should use this; it'll allow you to contact me here in Ironforge.