Samar
Delays in diagnosis can result in cells moving to other areas as well as initial site tumor growth. Probably not the best thing to think about right now.
More important is to not beat yourself up for using tobacco products and ending up where you are now. (It's great that you stopped and that you have not faltered. My father-in-law was dying of lung cancer and still could not stop.)
Now that you have the diagnosis, the hard part starts.
Develop a strong support system of people to help you over the next few months. Dealing with the surgeries and treatments can be quite stressful without having to worry about paying bills, housekeeping, work, and life's other daily stresses.
Set an area aside at your house / apartment for comfort. Blankets / place for meds / pillows / etc.
Get familiar with your health plan coverage or have someone available that you can count on to handle any insurance issues
Head and Neck cancers tend to be aggressive and the surgeries and treatments required to become cancer free are extremely hard on the surrounding organs and soft tissue
Focus on becoming cancer free and set goals or milestones on how to achieve it.
I think most people on this site will acknowledge how important it is to be emotionally and mentally prepared for the steps required to rid yourself of cancer. Don't get caught up in the numbers or drama. This is your battle. Be as prepared as possible.
Good Luck