Correct me if I am wrong but I understand that mold can destroy the coating on the lens.
If the lens is coated and the mold has destroyed the coating, no amount of cleaning will repair it. Only disassembling and recoating will restore it. Unless it is a rare and valuable lens, it might not be worth the cost.

I'm with onepuff. If the lens is cheap you could try to clean it. If you are not very successful you haven't lost much. You could still use it for parts to repair other lenses or you could simply use it for experimentation purposes.

Otherwise, find a better lens and save yourself the money and the trouble.