I'm not familiar with the Applebee's version, but quesadillas are one of the easiest things you can ever make! Simply use flour tortillas (available at any supermarket), and fill with anything you like. Just make sure you have enough cheese to hold it all together. I would imagine low-fat cheese, along with some chopped, sauted vegetables (onions, peppers, mushrooms, olives, etc.) would make a satisfactory quesadilla.

As far as cooking methods, this is the way I do it:

Have all your ingredients ready and at hand. Heat a large iron skillet and place one flour tortilla in it. Working quickly, spread approx. 1/4 cup shredded cheese on the tortilla, sprinkle your filling ingredients over the cheese, and cover with another tortilla. Using a large pancake turner, press down on the quesadilla to flatten it, and turn it over to brown the other side.
Place on a platter and cut into quarters.

After a few tries, you'll be able to customize the recipe to your own tastes.