A monster truck is exposed to wear and tear all the time because the driver uses it on the toughest environment. Of course, you can expect the dirt accumulating in it. Also, it would be damage since the driver just let the truck to crash anything on its path. Though, this is made for crashing, it doesn't mean that it doesn't take damage too.
That is what happened to your monster truck as you don't take care of it carefully. You never did drive it with safety in mind as you don't practice safety precautions when driving. Now, it is all dirty and it need repair.
The game is played via mouse and the idea here is to wash the truck till it is clean. After cleaning it, you would need to repair the outside part then you need to connect the cables to make it run smoothly again. Change the old tires with a new set of tires since it is all worn out. Change the color of the truck, but you don't need too if you are already satisfied. Put some decorations on the truck. Once that, you are satisfied then you can show the finish product.