You still have some armature modifiers :). They are not set up properly (no armature name) and they will not work in BGE (in BGE the skin mesh object must be parented to the armature).
The wrapper is a helper to apply the car physics. This is because it is really difficult to set up the car physics with rigid body constraints etc…
The VehicleWrapper is an Python interface (API) allowing to set up a car body and attaching wheels. You can configure some properties such as suspension, damping etc.
To make it drive you can add forces for brake, drive and steer.
All this things are available by Python function calls only. There is atutorialaround describing how to set up the scripts to use the VehicleWrapper API. You can check that if you want. Then you learn how to set up the parameters in python.
If you want to concentrate on modelling cars, you can use the template in the above thread, without worrying the Python code. This template uses the same API as the tutorial.