Hi, first of all you have to stop the habit of gutkha chewing. You can try engaging yourself in some healthy habits like chewing sugar free gums.. even nicotine chewing gums are there..its course depends upon how much gutkha you take per day.. Also nowadays Nicotine patches are available which can be pasted upon your body part (usually back - hair free part) ...this releases the nicotine over a decreasing rate and thus controls your urge.. But still you control your will power to stop the habit. For yellow teeth- you can get it professionally cleaned (Scaling )
Yellowish stains are cos of guthka.
You will need scaling & polishing for that. b it as you rightly said what you need to do is stop guthka.
where there's a will theres a way!! there are many like you have successfully stopped the habit. if so many can I am sure so can you. please use nicotex chewing gum to help you get rid of the habit. I am sure you will be able to do it.
Any stains on your teeth can be removed with cleaning (oral prophylaxis). Colour of your natural teeth cannot be changed with cleaning, it requires other procedures. Try a replacement to your habit. I replace it with a healthy one. Cancer should be taken seriously.