You should do much better selling it to a third party than trade to dealer. Dealers will not give nearly as much on a trade in, and I always recommend that someone trading get value first before stepping on sales lot. There is no truth to the idea you will get more if you buy a more expensive vehicle. The trade in value is one separate action, and the purchase of a vehicle is a completely different financial transaction. You negotiate each one separately, or you get lost in numbers. Different, but using this to say: Always! Always! Negotiate the sales price of a vehicle even if you end up leasing. You never, ever pay the price you see on the internet. And always negotiate the return value, your payments are based on initial sale price less residual value, so negotiate well and your lease will be much lower. The line of $199 a month with $3500 due at signing is just to get the 199 price point in the add, there is no law you have to put money down.
Back to the topic: The one thing you, the purchaser, can benefit from is the sales tax savings by showing the trade in value when titling your new vehicle. That is why you want to negotiate trade in first and get it as high as possible. The sales person will not let you leave even if you demand that value first, and don't fall for the "go look on our lot while our appraiser looks your truck over". Have them get you a coffee and donut.
Records would be possibly helpful to seal the deal to a third party but value is based on vehicle, options, and subtracting for above average mileage and wear and tear. Dealers will not care about records, they generally make a decision to wholesale out after trade in, or may further inspect and either then sell on their lot or otherwise wholesale if they find something.
