Actually the recommended change interval is 150,000 miles according to the maintenance guide. However, I think most of us will agree that might be too long unless the car is driven gently and has mostly highway miles. I would go with a 60,000 mile interval unless the car is severe service, in which case I would recommend 30,000 mile intervals.
The 2008 and 2009 Taurus has the 6F50 transmission that specifies MERCON V fluid. Later years switched to the MERCON LV fluid, but it is not backwards compatible.