Sergio is a great host! His place is safe and stylish and very close to Trastevere train station (5 min walk), from where a direct train takes 30 mins to Fiumicino Airport. From/to Ciampino Airport you need to take 2 regular buses (check Google Maps, very easy and regular connections), takes approximately 1 hour. To the city center it's a nice straight 20 min walk, but you can also take the tram. Will come back!