Walrus is dead on with his advice. I've done it that way numerous times. Key points to highlight 1). Change trains at Shinagawa station, a much smaller and easier to get around station. 2). Take a N (Nozomi train). Least amount of stops and faster door to door. 3) you can go online to the Japan rail central website (yes it is in English) and get the current timetables and fares. 4). They do sell food on the train but I recomend getting it in the station before you board.