employment-private property

The dealership is responsible because its employee did the damage while doing work for the dealership, just the same as it is responsible for the customer's car. As the vaule of the damage to your tool box, you should be paid for the replacement cost of the box and any contents that were actually damaged. You will probably need receipts to show the value. Small claims court can handle cases up to $10k, so you will have to file in a county civil court at law if there is no adequate settlement.