Ok, you’re getting a lot of advice from people who may or may not have any legal experience and I’m no better, but I have, however successfully (and quite easily) had things removed from my credit report, and have dealt with my own contact issues in the past and won (it was a rental, but we did manage to scare their lawyer into paying us to move).
In case that somehow gives my grain of salt advice more weight, I’d personally start by bringing it back to the dealer that wrote up the contact, and then pointing out, repeatedly, that it clearly lists that their is no overage charge on the contact you signed in their finance office. This may take an hour or so extra out of your life, but it’s likely going to be the end of it as they would then have to go through the process of explaining to the lender why the contact says what it says, and then the lender would have to want to go to the trouble of pursuing it.
If it’s not, and you have to deal with the lender, you’re in a strong negotiating position, and they will likely take pennies on the dollar if they argue with you.
If it goes past that and you feel like fighting, demand a small claims dispute in your area and you’d likely have a strong case.
If, however, you’re worried about it damaging your credit and this somehow goes through collections (one email to the collection agency with the contract attached would likely end that process before it gets to that point), if they try putting it on your files, all three credit reporting agencies have easy to use online dispute forms where you would attach the contract with a note explaining it to person who will look at it for ten seconds or so (unless it just gets removed automatically like many of them do when disputed - that’s how it’s gone for me thus far, anyway), and I sincerely can’t imagine it wouldn’t be taken off on the off chance it escalates that far in the first place.
Finally, if you want to completely get past this with no trouble and you don’t want to keep it yourself, put an ad up to sell it. Your ‘cousin’ that comes with you shouldn’t have any issue buying it out that’s exactly what the finance department told me to do on my current lease - the lender would much rather get rid of it as soon as possible.
Hope this was somewhat helpful