At first I had this down as total madness, I'm prepared to revise my estimate to just "pretty crazy".
They mention inflatable modules that would provide extra living space. Also since it's just a flyby that removes a lot of things that can go wrong with landings and orbital insertions.
Still, we have no experience at all of long term missions that far beyond the safety of earth. If it were to go ahead I would not put good odds on the crew making it back alive.