If we take a train from Shanghai to Beijing, how long would it take and what would be the cost?

From the Hongqiao Railway Station, there are bullet G trains to Beijing. The travel time is about 5.5 hours, and the fare is CNY553 for the second class seat, CNY932 for the first class seat and CNY1748 for the business seat.

How far from Beijing is the Great Wall and what is the best transportation to take there?

The great wall has several sections in Beijing, and the Badaling section is the most typical one, do you refer to that?
If yes, the great wall is about 43 miles to the north of downtown area. In the north railway station, there are trains to Badaling, and the travel time is about 1 hour.