You've past the first hurdle, you actually want to quit. Have a word with your friendly GP/ Practice nurse, as there is lot's of help available, and its usually all free ! Beware of "Zyban" and flying though. (It may cause fits).
Try to avoid the "gloom and doom its your own fault" merchants as they aren't really going to be much help. Most things carry a risk, and I would be no more loath to treat a smoker, than someone injured for not wearing a seatbelt in a crash.
Try "Quitline" on 0800 00 22 00. They may be able to send you some useful info !
As regards health risks, its probably the most risky thing you can do. I guess that your pretty young so you are probably getting away with it at the moment. Most people's respiratory function drops after the age of 25yrs, as evidenced by the "peak flow " tests performed by the AME. Smoker's resp. function tends to drop at a greater rate, but they reckon that if you get off the ladder sooner, you may regain normal decline after a few years.
Good luck, hope its useful info.