I was only there once we rode the quads in but we seen a older couple in there probably 60's stuck right as you get in they had a 4x4 full size pickup it just would not move so I stopped and helped them..
they said it was always on there bucket list to drive the dunes I thought that was cool
they did not air the tires down at all si me and my buddy aired them down for them but told them to be extremely carful when they leave and to make sure they aired them back up before driving to far, no idea how low we aired them down we did not have a gauge but it worked they spent the whole day cruising around made us feel good we helped them out.
imo stay out of there with a 2 wd truck unless you want problems