Good start, but focus on getting the details looking accurate. The biggest thing I see here is the edges are too rounded, which gives you the toy car look. They shouldn't be sharp, but they shouldn't be as round as yours either. Take a look at a real car, and you'll see that from a distance, all the breaks in the panels are nice and crisp. This is my biggest gripe with using SUBD's as using the crease tool lets Maya decide how the final product should look, rather than you specifically making the final object look real.

As for rendering, don't worry about it. HDRI's are a good quick way to get a decent snapshot of how you're doing. But once the model is finished, take a try at developing your lighting skills.