Most of the fat is probably in the cheese, so leaving that off is a good choice to reduce the fat. But, there are a lot better things you can eat for 320 calories.

Why, a Lean Cuisine lemon pepper fish has 330 cals and 70 cals of fat.
Why not make your own "lunchables"? It will be cheaper and you can choose the foods you want.

However, if you're out and unable to make that choice, omitting cheese is a good strategy.
Jay