When you smoke your cholesterol levels tend to get higher than normal and after three weeks of quitting smoking you should notice your cholesterol level lower to normal levels.
After three years of no smoking then you should notice a good normal level of cholesterol as well as blood pressure and when you've been smoke free for three years your risk of heart disease and heart attacks, strokes etc is less.
Quitting smoking is the best thing you can do for your health and you keep your heart healthy as well.