Go towards the marked area and enter the church to talk to the Rakyat leader. He will give you C4 explosives that you need to plant on the tank. Then, climb the water tower before the allotted time passes. There, you will find a sniper rifle that you need to use.
Start killing soldiers below. Also, get prepared for reinforcements that will arrive, right after you kill some of your enemies.
When you manage to kill most of the soldiers descend from the water tower and enter the truck in the left part of the village, shown in the screenshot. Because your time is limited, try and steer around the enemies that are still alive.
Drive out of the village, and towards the marker (turn left on the crossroads with the blockade). Try and steer around the cars going for a head-on collision. The truck you are after won't make it far. Once you find it, kill out all of the soldiers that guard it and open the back door. This will complete the mission.