Sounds like you have a claim against the dealer. Ask them to cover the difference.
In seeking an attorney on this site, beware of limiting your search to attorneys with a 10 rating, and carefully read the AVVO disclaimer regarding their rating system. There are certain factors that are given great weight which do not necessarily have any bearing on an attorney's experience, abilities, and results with certain types of cases. Accordingly, the rating numbers can be misleading. Also beware of basing your choice on the fee charged, as a low fee, depending on the skill, experience and determination of the specific attorney handling your case, could actually have an inverse relationship to the amount actually put in your pocket.
You can sue the other driver and the dealer in justice court. Depending on the amount of diminished value you can prove, this may not be worth the hassle. It is not practical to hire a lawyer; you'd spend more on the lawyer than you would get back and you can't recover attorney's fees in this type case.
This is not legal advice. You should always discuss the specifics of your issue in person with an attorney. Be aware that there are time limits on all claims that depend on the kind of claim, so do not delay in seeking an attorney.
Speak with the dealership and see how they respond--you could also file a claim in small claims court--good luck.
*This information should not be construed to be formal legal advice nor the formation of a lawyer/client relationship.
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