What is the ruling on benefiting from money that exceeds the cost of repairing car damages, and am I held accountable for the error of the employee if he made a mistake in assessing the accident?

The one responsible for assessing errors in accidents is more knowledgeable about the laws. Therefore, there is no blame upon you for accepting his ruling, unless you are certain that you are the one at fault. If you are certain that you are the one at fault and a ruling is made in your favor contrary to the reality, then it is not permissible for you to obligate others with what they are not obligated to do, for the judge's ruling does not change the reality of the situation. The Prophet, peace and blessings be upon him, said: "You bring your disputes to me, and perhaps some of you are more eloquent in presenting their case than others. So, if I rule in favor of someone concerning the right of his brother based on his words, then I am only cutting for him a piece of hellfire, so let him not take it." If you are entitled to compensation, there is no blame upon you for benefiting from it as you wish.