Thanx Michael for your advices.I can see it much clear today.I will continue to model smaller things to sharpen my skills.Then I will try another aproach to build a car with moi3d.I watched some car tuts here on your forum,and also I saw some rhinoceros tutorials.Thanx again for your guideings.

It's not exactly nurbs but...from nurbs to nurbs ;)

...and how is this different from poly modeling?

Try this to help you out.

http://www.suurland.com/tutorials_newbeetle.php