No the timing belt does not have to be changed but you do have to remove it to get to the water pump so i would recommend that you do so and also replace the tensioner, i can't tell you a price because i don't where you are i am South Carolina and the parts alone for t-belt ,water pump and tensioner are about 150.00$ cost from Ford (list is a bit higher) and about 3.5 to 4.0 hrs labor at a shop