actually, since it isnt a "race" some of your own insurance will cover whatever happens.
including injuries, and damage to your car.

like the guy at the autocross that hit the pole, and fire hydrant.
event coverage handled the damage to the place, his own insurance covered his car.

also, you should have your own medical insurance REGARDLESS of what youre doing. racing, or just being alive.

relying on any event promoter to handle your medical expenses if you wreck is pretty ignorant.