Saute chicken in a medium saucepan over high heat for about 20 minutes or until internal temperature reaches at least 165 degrees F. Add vinegar, lime juice, sugar, salt, pepper, green onion, garlic and oregano. Simmer for an extra 10 minutes. Heat an iron skillet over medium heat. Place a tortilla in the pan, warm, and turn over to heat the other side. Repeat with remaining tortillas. Serve lime chicken mixture in warm tortillas topped with tomato, lettuce, cheese and salsa.