When you take it in for an under carriage inspection there should be only a flat fee for inspection, most places charge a 1/2 hour or an hour, times their flat rate, which is around $30.00 for a 1/2, to $150.00 for an hour, depending on the facility, and there are places that will do it for free. You may want to consider claiming any damages on your car insurance depending on your policy. Also you could go to Jiffy lube, get your oil change and look under the car yourself, and then ask some questions about things your not sure of, { the stuff that looks like it was damaged }