Can someone provide me some information on car rentals in India?

I am going to travel to India this summer and would like to drive. I checked out major auto rental sites and they seem to rent cars in India in major cities. The questions I have are:

(1) What kind of driver license is required to drive in India?
(2) What kind of insurance is offered by the rental company? I have seen a lot of fender-bender in India.
(3) Do the rental car companies offer drivers for an additional fee? How much more money are we looking at to add a driver?
(4) Are there any GPS devices that work in India and provided detailed maps of major cities and highways?