Most of the levels are easy and straight forward that they don't really require a guide. There are however 2 levels that I'd consider to be very hard, Oyster Harbor and Diamond Sands.
(For all the Main levels I would recommend you end the level by entering the truck as soon as you clear the path as this will help the time trials you need to complete to unlock the ability to get platinum)
1. As soon as you start this level pick up all of the ammo crates and make your way down to the oddly colored grass and start shooting the freight containers you only need to destroy the first 2 groups.
2. Make your way NW and you'll see a ramp that will take you down to the lower level, walk over to the bulldozer (You may need to walk around the freight containers) and destroy any containers left. Slightly north of where the Bulldozer is there is a crane and a whole bunch of TNT, hop in the crane and put a TNT crate onto it, It is crucial that you put the TNT in the dead center of the structure as that will destroy the entire thing (and not just a section).
3. Ideally you want to beat the Carrier across the path you just made, (if you don't, don't worry just go around the long way)
Read the next section before you start it.
4. Next up are holes in the ground there are square and diamond ones, start by filling the first square, then destroy both buildings nearby and fill the second square, NOT THE DIAMOND! (if you put it in the hole it was next to then you need to restart) Behind the buildings you destroyed there is a pathway blocked by a hole, move the diamond block into this one this will give you 2 more diamond blocks, then move both of those into the holes on the main path. There is a square to the left of the 2 holes, and the last square is to the north behind the giant Gas tanks. then destroy the small factory looking thing.
5. Go across the first boat then turn left you will see a second one, drive across it and ignore it for now and park the Dozer on the third, reverse the boat into position. Drive to where the second boat needs to go and you will see a foot bridge, walk across it then to the second boat and reverse that into place and then get back in the dozer.
6. Park the Dozer on the first boat (make sure it isn't in the way).
If the Carrier hasn't reach the holes you filled then continue as fast as possible, if it has you will need to wait until it has passed the first boat (pull down the right stick to check don't drive towards it)
Drive the boat all the way forward and you will see another dock that has a TNT on it, very quickly push the TNT onto the boat. Now drive the Boat back. You will need to push the TNT across the boats and into the large building at the end. (If you had to wait for the Carrier be extremely careful)
This level is straight forward but I found it hard due to the vehicle you have to use. All I can say is make sure you know how to use the Dump Truck effectively and focus on one building at a time. When you start go to the opposite side of the tracks first before you start to destroy the buildings, the reason is that you will need to be on the left side of the track at the end of the level to destroy the final building.
As soon as you destroy the final buildings at end the both of the levels, immediately get into the large truck and end the levels so you don't have to repeat them later in the time trials.