I start most people with 30 min, 5 days a w. We start with slow steady state, walking on a treadmill on incline of 3, walking about 3 miles an hour. You want your heart rate to be about 120-130 BPM. This is where we start. If he is not getting the results I want, we will add more or increase to more cardio, a second session or make part of his cardio HIIT.
As for diet, everyeone is different. If you are interested in having me write a plan for you, let me know. I can be contacted through the Next Level Nutrtional section of the Naps site. In general though, you need to eat less cals than it takes to stay the same. So figure out what it takes to grow, remain the same and then, it will be more easy to figure out how to reduce. If this all sounds like a lot of work, just hire me ;)