I am still going through the process, hoepfully tomorrow I will have a better picture. Anyway as far as I know this is what you need to do.

1) If you have fully paid the car and you have a buyer to buy the car, you have to change the insurance to the new owner first, you may require ID copies of the seller and purchaser, fill up the form and pay QAR 50. then you go to Madinat Khalifa to change the car ownership. I am not sure what is the requriement.

2) If the car is still on loan, you need to pay full amount of the outstanding balance, wait for a day, get a release letter from the back for the insurance and traffic department. Bring the release letter and the both ID copies as (1) above to insurance company and change the insurance and finally to Madinat Khalifat to the change of ownership.