A friend has a 12-hour layover in Incheon/Seoul coming back from a trip early next month. She found out the airport offers a free guide to take you around the city to see some sights. You sign up at the airport. She also heard you can hire a sightseeing guide for a fee but hasn't researched that yet. She's an older lady, will be by herself, and wants to be sure she'll be safe. Does anyone know anything about these options or can make recommendations?