Is this a valid civil case that has high potential?

A diminished value claim has a better possibility of being successful the new the vehicle.  Also, you should try to make the claim against the person's auto insurance company.  You need to obtain written documented proof that you vehicle has a diminished value as a result of the collision with the tractor trailer.  This needs to be obtained from a property damage appraiser.  Try to find a company in your area that is willing to provide written documented proof or I suggest the following company: Reed Appraisers (301) 946-6116 www.Reedappraisers.com Keep in mind that some auto insurance companies will consider diminished value claims and others will not.  Also, some auto insurance companies are of the belief that you cannot have a diminished value claim until you sell your vehicle and then prove to the auto insurance company that the vehicle sold for a lesser price because of the vehicle having a diminished value.  But most insurance companies will consider a diminished value claim once you obtain a written report from a company like Reed Appraisers.  Good luck with this matter.