It would be helpful if you let us know what your eating is like now, so we can make suggestions for change that would be healthful and help you lose weight, but not be too drastic.
I agree that good abs are much more than just ab work. One of the best ab exercises is actually squats, because they use a lot of muscle, and therefore a lot of calories.
Ab and core work is important for back health, and to support your other muscles when you work out, but rather than spend too much time on abs, you'd get more bang for your exercise time by doing resistance work for large muscle groups.
For cardio, 1-2 interval workouts a week are a good addition to a program, because they are more efficient than steady-state workouts (just don't do them two days in a row, or more than 2 a week).
And, of course, a clean diet. Every time you eat, you always have a choice of what you are going to take in. By making the best choice (or at least a better choice), you can make good progress.