A gunman shot and critically wounded a personal aide to PLO chairman Yasser Arafat in an assassination attempt in the southern Lebanon port city of Sidon Tuesday, a militia official and security sources said. Initial reports from Sidon said Issam Salem died while undergoing surgery after the attack, but that report later was discounted. There were no claims of responsibility for the attack. The security sources said the would-be assassin, using an automatic rifle, fired several bullets at Salem as he was shopping in broad daylight in Sidon, 24 miles south of Beirut. Salem, also known as El Loah, was hit and seriously wounded in the head and was rushed to a hospital.