Diesel is going for $2.899 here, but $300.00 would be about right. As for hills, no significant ones on this entire route. Wind would be a far more significant factor depending on which way it blows.
David and Shirley -- East Texas
2955 RL Montana
Chevrolet Duramax 2500 Allison Trans
http://www.dwilliamson.com/mont.jpg