Thanks so much all of you for your helpful suggestions and comments.

Last night, after deliberate thinking, I returned the car to the rental agency, and told them that it was my fault. The rental people told me that the car has got some kind of insurance (quite basic level I suppose) and there is an excess of QAR 1000. I dont know anything about insurances, but I guess it means that if the total cost to do the denting & painting (as per rip-off workshop prices where all rental cars will go) is suppose QAR 1800, then I'll pay the first QAR 1000 and the insurance will pay the remaining QAR 800. Is my understanding correct? So does that basically means that I practically have to pay maximum of QAR 1000, and the insurance will pay the rest? Cheers