There's a bar and a good grocery store in the Arrivals area, both opened 24 hours. If you end up waiting for your flight, it’s better to go to one of these two places (by the way, you can plug in your laptop there). The departure and arrival area outside of the check-in area have a few 24-hour food and souvenirs shops, pharmacy, cafes (a meal for about $10, drink - $2-$5), bank and exchange offices.
An express train runs every hour from Savolovsky Station to Lobnya, where shuttle buses continue to Sheremetevo. The complete trip takes 75 minutes. A taxi between the airport and the city center takes 45 minutes in light traffic and costs about 800 roubles.
A taxi to the center of town should run $50-60, but be prepared to haggle as drivers usually suggest you pay more. The bus-metro combo is a budget alternative, it costs just $1, but service stops at 10 pm. Take bus 551 to the Rechnoy Vokzal metro stop and a catch a train going into town.