Patriot's Hangar
Walk forward and up to the gate leading into the hangar proper. You'll hear a guard talking about how he lost his key card. Wait for the conversation to finish and you'll see the guards break up to search. Most of the guards will walk to the right, even if they walk left first so make sure they walk right and that the truck on the right breaks line of sight before moving.
Take cover at the tale of the hangar and walk around the side towards the trailer. Pick up the Wrench on the ground and then make your way into the boxes against the wall. Follow these along until you are behind the trailer. You'll see a crate that you can dump bodies in at the corner. From here, look at the Patriot and you'll see that there is a chair near him with a Teddy Bear sitting in it. You can walk right up to the teddy and grab it.
Take the teddy and then return to your corner. After a little while, The Patriot will freak out and send his people looking for it. Once they spread out, toss the wrench a little bit shy of the crate so Patriot can hear it. He'll be the only one around and come to investigate. When he does, subdue him and steal his outfit. Drop his body in the crate and get ready to fight.
Before we leave, there's a piece of Evidence in the far corner of the hangar from where you entered. There will be a guard here that doesn't move but you'll be in costume so it shouldn't be a problem to grab it. Head back in the direction that you entered from and watch for red double doors on your right. Walk up to them and you'll knock on the door. You'll put your weapons down and then walk to the ring. Take the walk and enter the ring.
The Arena
The fight with Sanchez is actually quite predictable. The first set goes - B, rapidly tap X, Y. The second set is exactly the same as the first. The third set is just the B button. After a quick chat, Sanchez will get up and you'll fight one last time. Repeat the pattern one last time to finish the fight.
If you happen to get hit, you can simply reload the checkpoint to start the fight over. Leave the arena when Sanchez is done and make sure to grab both of your guns before leaving.
