You're very welcome Vyas.
Bright sunlight is horrible for car shots -- it produces hard shadows, and specular reflections that are likely to degrade image quality (by introducing flare). Best natural light to photograph under is what we call directional diffused light (think "overcast day, but with one area of the sky being brighter due to the dun being behind it).
In terms of resolution, for a given camera, it's really a moot point because the camera has a fixed number of pixels (unless you want to photograph the car in sections and electronically stitch the images together to make a higher resolution image). So if you can only capture a given number of pixels - and you need to print at a certain size - then "it is what it is". You can't create more pixels and you're not going to throw any away - so in essence it's a done deal. To put some number to that though, if you used a camera like the 36MP Nikon D800, you'd end up with (assuming no cropping) with 7424 pixels, spread across 78 inches - which will give you 94 dpi. If you were viewing a 94DPI image from 1 or 2 meters away then you'd be able to see a bit of degradation, but from 7m it'll be fine. In reality, correct sharpening will have a much bigger impact on final image quality when viewed at that distance. Does that make sense (sorry, it's a topic that seems to confuse a lot of people for some reason).
1 year will give you a lot of time to practice
Tell me though, is it just car exteriors? Or are there also interiors?