Man I think that is off to a great start as far as the design.
It still looks like a cartoon though. I would just increase the wheelbase to 2-2.5 wheels widths.
Here is another link on drawing wheels.
http://www.drawthrough.com/tutorials/index.html
Great job so far.
As far as shading and rendering there are some helpfull links at the top of the forum.
Basically what I would do is find a good magazine w/ nice images like MotorTrend or Road & Track and look at a car w/ nice reflections (study it) and then reproduce what you see using a pencil.
You can also go to their websites (car mags) for free images.
Here is a shading tutorial, even though it is for portraits it applies to cars. Look at all the links. Notice Capt. Picard's shiny forehead, the same techs. and styles apply to autos. Mike Sibley's link is a great place too.
http://homepages.tesco.net/~p.wilkinson/index.html
I hope that helps get you started.
Welcome to the forume.
alfred