Yes, its a scam. Its the Overpayment Scam. The way it works, the scammer offers to buy your item for your fill asking price. He want the item to be shipped somewhere. He pays you the shipping fee, which you wire to the shipper he chose.
The scammer sends you a notice that the money is in your Paypal account, and you immediately wire part of the money to the shipper. They you discover that the notice was fake and your Paypal account is over-drawn. Or the scammer sends you a certified check and you wire the money. The check bounces because its fake and you owe $$$ to the bank where you cashed it.
The scammer and his friend, the shipping company vanish and cannot be found. They split the shipping fee.
The scammer communicates only by text and email because he speaks with a pronounced foreign accident, often African or Indian. He doesn't want you to know that. The scammer's local police do not cooperate with US law enforcement. The scammer will not be caught.
I listed a car on autotrader. Almost immediately after it posted I receive a ttext. The text basically asked if the vehicle was still available in broken English. He asked for me to email. I thought it was odd but I emailed him saying simply, yes that the vehicle was still available. He responded saying he cannot communicate over the phone because he is a "sailor" and his wear abouts are top secret lol. He said he would pay full price and have a "mover" pick it up and that his son graduating college is super excited because it's just what he's always wanted! The vehicle is a Ford F-450 flat bed work truck. Not the everyday driver you dream about. Beware of this guy!! It's a 100% scam!