Loading a 3D model car in opengl

When it comes to loading a 3D car, in opengl, do I have to load the car with the wheels or do I have to load them separately? You know, load the car, then load the wheels and then place them at the specified points, because I want to steer those wheels and to animate them.

I am fairly new to loading 3D objects in raw opengl, I was able to load a tree, which is a simple model.

Thanks!