I've taught cookie classes before. And the answers to your questions really vary from teacher/class to teacher/class.
In my cookie classes, we usually do a project. I make all the cookies for the class, bring all the containers, fondant, the works. Then they get to ice and decorate thier cookies, then place in the container(if doing a cookie bouquet) i do show how to roll out the cookies, they get a recipe and they get shown how to cover a cookie with fondant. Introduced to food markers, fondant lace, and textured rolling pins.
I only teach one to two classes a year, cause they are so much work for me, and i don't end up getting paid enough to make it worth my time.
Class time usually runs two hours.
I teach them all the time. I teach one monthly at a nonprofit cancer organization, I teach several different kinds in adult continuing education Fall and Winter semesters. I also give private lessons and have taught by special request at various functions.
Each of those situations was different, but generally the classes run 2-3 hours and we cover the lesson in that time. I've broken them up into the beginner and advanced classes (advanced using white chocolate, fondant and edible jewelry/molds) and have also done chocolate on cookies classes. For the paying classes, I provide everything including the cookies, fondant, chocolate, etc. and the molds and such, textured rolling pins and whatever else we're using. Students bring a box and in the paying classes pay me a provider fee which is different than the tuition.
Would I do it again? Absolutely!! It's sugar -- it's FUN!!! 
I think a cookie class would be lots of fun! I think making cookie bouquets would be a good class topic.
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