Ralph is tied in the upper level of the slaughterhouse/ meat packing factory. There are several sentries in the ground floor and one more in the second floor. There are multiple entrances in the factory like going to the front door, climbing cover a trash bin and over the fence from the west and breaking in there, or entering from the parking lot from the east. There are also multiple workers here that won’t give you any attention or alert the gang members but still use your Intel View frequently to identify the targets.
There’s a tac-vest in the southeast corner of the factory, and some medicine cabinets in the other corners. There’s a lot of cover and corridors here that will allow you to move easily and perform steal kills.
Make your way to the second floor and use your intel view to locate Ralph. If you're following a stealth approach, the challenge you'll encounter is the two guards talking in the middle of the path. Find cover and let them finish their conversation. Once they separate, whistle to isolate one of them and take him out.
Next, stalk to sentry walking around then use your intel view to find Ralph. There are only three guards around him, all facing away to each other so you can still wipe them all out with stealth kills if you want. Once clear, free Ralph to complete the mission.
Before leaving the warehouse, loot the cash stacks as marked in your minimap and collect the Vargas painting inside the office and rip off the Propaganda Poster outside of the slaughterhouse.