How to do a digital rendering

I have been wanting to learn for a while and have recently learned how to use Illustrator. Anyone have any tips on how to do this?
 
Here are my questions::
 
 
1. Do you start with a picture of a car you are wanting to do?
 
2. How do change the color of the paint?
 
3. Shading on the paint?
 
4. Graphics on the paint?
 
Anyone want to give me some pointers on what to do or links that might help me would be great. Thanks
 

photoshopchop.com  can learn alot there.

you wanna use illustrator, cause the questions your asking sounds more like you need to use photoshop...