Here's how the doctor explained it to me. When you're born the lung start @100% then as we age it dips slightly. So a 25yr old that smokes often would be @like 75%, as opposed to say 80%.. However the lungs are one of our most regenerative organs. Upon quitting your lungs will heal back up to the % equal to your age. That's for the lungs though.
You probably will do better in that department as the lungs clear the debris from your lungs. It takes time, but it does improve. There might be a residual cough from the years of smoking. My sister was much like you but did quit...her lungs are so much better and she definitely has lost that smoker's cough.
Good luck, I hope that you are able to stop
Jenn