I travel to NJ a few times a month and this is quite an easy trip. Though i do speak Chinese, it should be a very easy process for non-Chinese speakers. Shanghai has two major train stations, and most if not all Nanjing bound trains will leave from the Northern station (North of People's square, across Suzhou creek). If you get the hotel to book your tickets and to tell the taxi driver where to go, you should have no issues.
Then once you get to the train station there is only one entrance to the platforms. It is somewhere in the center of the building, just across from the main square (big tv screens, lots of people). Your taxi may not stop directly infront of the building entrance, but you will easily see it.
You then show your ticket to a guard who will then let you enter. Bags go through a quick security check and you then take the escalator up to the waiting lounges on the second floor. All the times i've traveled to NJ the waiting lounge has been lounge 4, on the right side of the main hallway on the second floor (don't worry, signage will be present and the waiting area will be easy to spot as long as you know your train number).
Once your train number is called, hundreds of people will rush for one small door at once. Just relax, the train won't leave for another 15-20 minutes. Then follow the masses to the train, get on, and enjoy the 2 hour 20 minute ride to Nanjing.

Trains to NJ are about 90-110 RMB one way in first class. Very comfortable seats and a very smooth ride. There are a few trains every hour. NJ train station is right downtown, next to the Xuanwu lake. Plenty of cabs, IIRC the taxi line is downstairs where you exit. Remember to watch out for illegal cabs.

Hope it helps.