You'll find the survivor named Damien on the way to the military base to the west. Climb the ladder up to reach him. There's also the Deathstalker Mod behind him.
First, you have to find him a battery in the immediate area. Next, you have to find him spark gaps in the marked locations. Head to the nearest one, the area southeast of the cinema. You'll run into a survivor there as well. Rescue him first then find the spark gap in the workbench past the rooftop by the canal.
The second spark gap is located northwest of Owen's shop (near the quarantine zone), by the trash cans.
After returning the spark gaps to Damien, he will ask you to get some coils inside the military base. (in progress)
On the Edge
You'll find the NPC named Ryan in the rooftop south of the church. Remove the blockade in front of the door then enter the house. Explore the room and kill the zombies inside. Breach the door in the far end of the hallway and clear the last room to find the medicine on the shelf.
Exit the house and kill the infected Ryan to complete the quest.
Head to the makeshift hospital south of the church and speak to the intercom. Once inside, go upstairs and talk to Dr. Cecil. He will then ask you to check the power box in the basement. Go to the basement and remove the barricade on the door. Kill the infected and proceed inside. Clear all enemies and activate the power box to update the quest. Before going back to Cecil, grab the Sticky Bomb Mod blueprint in the next room, behind the door beside the power box. Talk to Cecil to update the quest.
You'll have to get a fuse in Greg's Place on the way to the army base. Kill the infected owner inside and grab the fuse from the toolbox. Return to the makeshift hospital and replace the fuse in the power box in the basement. Turn the power back on and talk to Dr. Cecil.
After completing “The Darkness”, talk to Dr. Cecil again to receive this quest. Head to the pharmacy to the west of the city and search the shelves. Your quest will update then until you gain access to the military base. (in progress)
After completing “The Darkness”, talk to Sean to receive this quest. Head to the southeast portion of the town and enter Stan's house to find the surgical kit. Once inside, find the doctor's room and kill the infected doctor. The surgical kit is found behind the table in the living room. Return to the makeshift hospital and hand over the surgical kit to Sean.
You can find this NPC in the northeast alley of Villa Henderson. (He appeared there after I completed “The Darkness”, so I'm not sure if that's a pre-requisite) He'll then ask you to find the Super-fish, Super-cape and Super-shoes.
Head to the southwest portion of the map. You'll find the dirty white super-cape past the small corridor of t-shirts.
Continue to the market to the southwest corner and look for the shoe, near the ladder leading to a workbench and merchant.
Finally, the super-fish is found in the fish stand in the fish stand. Deliver the items to the zombienator.
Follow Eddie and kill the next wave of infected. Find Eddie back to his original position and talk to him again to get your reward.
The Dead Can't Dance
Talk to Eva in the terra of Villa Henderson. Once you received the key, go to the restaurant below and enter it. Close the door immediately to avoid getting overrun then turn off the radio. You now have to turn off the power switch outside to disable the alarm. It is found beside the ladder leading to the terrace where Eva is hiding. Turn if off then talk to Eva to complete this sidequest.
You'll find Jorge Tesoro inside the workshop west of the Sea Market. Clear the undead outside then breach the door and talk to him to accept the quest.
Fast-travel to the Henderson Ferry Station or just walk your way to the bank. Enter the bank and eliminate the zombies in the first area. Kill the thug and loot the vault key from him. Make your way to the vault and you'll find Michael Dimes. Talk to him to update the quest then return to the first floor office. Use the computer there to track the GPS. Make your way back to the Pinai Ferry Station.
Follow the trail until you find the bandits. Kill them both and loot the treasure from the back of the truck. Return to Jorge to complete the quest.
After completing the sidequest “Perfect Plan”, you should be able to trade Diamonds with Jorge. There recurring diamonds in the Henderson Ferry Station and in the cinema base camp. This is a repeatable quest.