First, drive down to the Port Authority. Find the Skipsun boat storage office, and go in to start the mission.
You're now at the auction. Walk through the hallways following the man showing you around. If you poke around the rooms here, you'll find an Audio Log to listen to.
Get to the end of the hallway and open the door and you'll find yourself in the main auction room.
Keep following the man through the room then up the stairs. Go upstairs and over the walkway.
Iraq will leave Mr. Quinn's room, so quickly scan his RFID tag as he walks past.
Listen to the old man, then head back and into the other room up here.
Once in the room, go down the stairs.
You'll find an audio log down here. Once down, drop through the floor.
Make your way through the tunnels down here, avoiding or taking out the guards. There's plenty of spots to hide from sight if you don't want blood on your hands.
Sneak back up by climbing the ladder down here, then make your way along the wall.
You'll find a speed boat, so hide behind that, then go through the open door.
Climb the stairs through the door, and take the bag of Weapons at the top of the stairs.
Hack into a camera through the fence, then hack the door open. Make it through, and you get tackled through the floor.
Everyone is shooting at you now, so when prompted, blow them sky-high.
There are plenty more men shooting at you from the other side, so take them out as well. The door in the fence is locked, so find the box to unlock the door, then head through. Take cover behind the pallets, and hack into the cameras in this area. Kill as many men as you can just using the hacked explosives either on the guards, or by where the guards are standing.
"Once the area is thinned out enough, go through and finish up taking everyone out. As you get to the end of this alley, an Enforcer will come out. Take cover and wait for him to walk right onto an explosive plate to take care of him easily enough. Make your way back to where the Enforcer came from, and you'll drop down into what is basically an arena.
"A garage door opens, and a ton of thugs start coming out. Great. Use the cameras to cause as much damage as you can, then go past the garage door to a lift that you can take up to the second floor of the warehouse.
"You can take the time to eliminate all of the forces here, but it is easier to just run away.
From here, just run. Hop down to the ground floor and open up the back warehouse garage door.
Run into one of the cars out back, and drive away as fast as you can. Nice!