Seize Spugmay Keep
You can complete this objective when playing the mission for the first time. It does not require too extensive a walkthrough, because you only need to kill, or restrain, all of the enemies in Spugmay Keep. Try to do this before jeeps with reinforcements arrive in the ruins, because they will make the task more difficult.
Obtaining the film before reinforcements arrive
It is not easy to complete this objective, because reinforcements arrive in Spugmay Keep seconds after the mission starts. Of course, you can head towards the ruins immediately and try to secure it very quickly, but this is risky and, additionally, it requires good gear (e.g. the rocket launcher, to eliminate the enemies).
If you are not geared up enough, or you do not want to take the unnecessary risk, you can adopt a different tactic and stop the two jeeps with reinforcements when they are still on their way. The first one appears in the Northern end of the map, close to outpost 23. The other one appears a bit later, in the South-Western part. The easiest way to destroy them is use the rocket launcher or explosives, but you can also do this the oldschool way, place an obstacle on the road and have them stop. Regardless of what you do, use the D-Horse and right after you stop the first jeep, head towards the area where the other one appears.
Extract the prisoner from the Eastern outpost
It is best to rescue the prisoner only when you are replaying the mission, because after you find the film, the area of operation gets limited and you will no longer be able to reach him then. You need to head towards outpost 24, i.e. the one in the Eastern end of the map. The prisoner is inside the building shown in the above screenshot and before you carry him out and fulton him, deal with all of the enemies around.
Extract the rare vulture
It is best to extract the vulture after you have found the film container and after you have secured Spugmay Keep. Remain in the ruins and note the birds circling around in the sky. Use binoculars or scope of any rifle and locate the rare vulture - it has been shown in the above screenshot.
To get the vulture down, it is best to use the sniper rifle with sleeping ammo. If you do not have it with you, wait for the vulture to land on one of the pillars, or on a lower ledge, and use a pistol. Regardless of what you did, you need to make sure that the vulture drops into the area where you can access it, attach the balloon and send it away.