Rookie question

I am bidding on a grading job. The customer is not going to have it staked. They told me to handle everything. It is pretty straight forward I think. Basically, building a practice field from a sloped area. It will be exactly the size of a football field. From one end to the other there is approximately 7 ft difference in elevation. Am I to believe that to make it basically level that there will be approx 3.5' cut on one end and 3.5' fill to the other? The grade is fairly constant from the one end to the other. In other words, there are no hills or anything. Just a constant slope. The material will be sandy material. How would a guy figure the cubic yards on something like this. I am also researching this in my books. Just wondering what your take will be on this job. This is just an open field with no obstructions. Thanks for the input on this.

Bill