By Russell Myers The Duchess of York will bravely use her skin cancer diagnosis to drive an awareness campaign on the importance of checking potentially harmful moles. Sarah Ferguson said she would turn her “distress into a positive” after doctors told her she was suffering from malignant melanoma, which is the most serious form of skin cancer. The Duchess revealed to friends she will use her time and profile to spur others to get checked, in honour of pal Carolyn Cotterell, who died from the disease. Fergie lived with Carolyn before her marriage to Prince Andrew in 1986. She died from skin ca…