On Island Harbor, where you spawn, stand with your back towards the boat. Start walking left along the coast. Walk past two or three hill ridges till you reach an open beach like area. Start walking inwards till you see the garage at distance. (Congratulations! You just found the truck). Start walking leftwards of the garage until you reach a lake like thing.
How to get Metal fragments?
Use the furnace, put wood and metal ore in top row, click "start". After some time, the metal ora gets converted to metal which is placed on the bottom row.
Instant house
Instead of building a house, go to Loot Island. As soon as you land, look up and to the left just a bit. Go to the brick building and live there. Place your house items around the loot trunks. When you gather the loot, the trunks will disappear when you save. DO NOT store your own items there or you will lose it. Trunks reappear every once in a while right in your home!
Vault Door, Replacement for airplane?
Once inside the vault (code is located @ closest farm, thanks to Game FB page) there is a red button in between two server stacks as you enter the computer room. You can push it and it calls in a missile back at the surface. IDK if this is repeatable after a certain time frame or not (having just done it myself). Anyone who learns more feel free to update.
Best place on Harbor Island...