DON'T GIVE HIM A DIME BACK! I had a garage business for over 10 years and there is no way it would cost more than a couple hundred dollars to fix back up lights. As far as rear window leaking - I didn't look at your pictures closely but if it has sliding rear window they always leak a little if you pressure wash a vehicle or something like that. If they are leaking from just rain it is likely the little drain holes in the tracks just have some dirt in them and would be a 10 minute fix. Hell a new window wouldn't cost more than a few hundred dollars. GUY IS JUST TRYING FOR A BACK END DISCOUNT.

As far as tags - report them stolen and be done with it. Just go to State Police Barracks - tell them what happened (short story no need to get into all the BS). "Guy bought truck & used your plates to get it home - never mailed plates back to you - what should you do about stolen plates". They will advise you how to proceed. I am sure you are not the first person to have this happen!

One last thing - reading your post again - I didn't realized the guy was from Princeton, NJ. DO NOT GIVE HIM ANY MONEY BACK - what he is trying to pull is why "old money people from Princeton" have money. Years ago I had a VERY HIGH END landscaping company in and we worked in Bucks County, PA as well as Central NJ. I NEVER returned calls for estimates or anything from anyone from the Princeton Area. They are notorious for pulling shit when it comes time for payment so we avoided the Princeton Area at all cost.

Typically most houses we worked at cost in excess of $750,000 and we were installing $50,000 to $100,000 landscapes. The majority of our work was in Bucks County, PA even though our business was based out of NJ. Knowing several other guys in the business fairly well and hearing some of their Princeton stories I wanted no parts of that area. The only two jobs I ever took near Princeton both turned into a HUGE mess when trying to get final payment. After those and hearing other stories we decided to let someone else deal with those assholes. We actually walked off both Princeton area jobs mid way through when owners refused to make their next progress payment on their projects. One guy did take the time to sue us and we won since he basically didn't follow our contract. NEVER AGAIN!