I have been there! I gained over 50 pounds when I quit smoking and am in the process of trying to lose that and more. Looking back I wish I would have been more strict with myself, you know not eat the cookies, chocolate, etc.
The only thing I can suggest is maybe chew gum, suck on hard candy, be really strict with yourself. If you can change up your routine, like if you smoke after dinner-go for a walk, if you smoke in the car-hold a pen or pencil. That worked for me as far as the quitting part. I didn't try at all when trying to watch my food choices, I guess I thought back then that I would never gain all of that weight.
Good Luck! Be strong! You can do this!