I worry more about these friend of a friend type of sales.
I would find pictures of genuine models just to compare to be sure all is correct with the watch.
Worry less about papers and concentrate on the actual watch as that's where you money is going. Box and papers worth maybe $350
Also make sure you get a bill of sale from the seller and have it include his name, address, case numbers. Signed and dated. Drivers licence # also a big help
Just be careful