Do people normally gain weight when they quit smoking?

Common, not 'normal': Yes, it is often true but it need not be. Smoking does raise metabolism - but there are other ways to substitute for it: exercise, water, spicy foods, smaller frequent snack/meals, black coffee, green tea are a few. Also, the intestinal flora does change but the impact may not be too bad. If you do gain a bit, you can lose it later. Your smoke level is low - it'll be fine. Best to you!