Quitting smoking will do more to improve your health than anything. Nicotine gum, lozenges or patches will help relieve the cravings while you deal with the habits and rituals of smoking.
Yes, you are still putting nicotine in your body, but not the carcinogens and carbon monoxide from smoke. You can cut down and eliminate the nicotine once you are out of the habit of smoking. Quitting smoking is easy--I did it thousands of times! lol I stayed quit by using the nicotine lozenges, then stopped those later by decreasing over time.
Keep increasing your walks to improve strength and endurance (this will really improve once you stop smoking)
Speedgoats <------yes!