Just my two cents:
1. Better return the car to Hertz as is and Hertz should provide you with another car.
2. For your own safety, I would advise agaisnt it.
3. Since you are fully insured, I beleive you do not need to make any payment in this case.
4. Should not affect your insurance, since a strong argument can be made that the accident occurred beyond your control.
Good luck!