No guns are required. When the mission begins, go backwards and then south along the back wall. Open the big doors and hop on top of the boxes, then over the wall. You should see a VIP guard go into the house. Sneak up on him, sedate him, and take his uniform. Go upstairs and stand by one of the doors (not the one in the middle). Making sure both of the guards are not looking, pick the lock. Go inside and find Delgado playing the cello. Fiber wire him and go out the door you used to enter, then get out of the mansion and go to the doors of the wine cellar/cocaine plant. The other Delgado will be talking to a friend. Follow Delgado into the cocaine factory, then out and into the other room where he seems to be doing lines of cocaine. Lure him over behind the barrels with coins and poison him. Hide his body in the case and go back into the factory, where you will find an elevator around the corner. Take it to the hanger and escape.