Alright. I have a lot of free time on my hands, so let's go.

1.) HPS's are great for flowering, you might want to look into another light for vegetative though. Especially because they will need seperate hours. Fluorescents WILL work, but if you're going for quality and have the money, go for a high-powered metal halide light.

2.) There are many different methods to keep the area cool. You will want to have at least one oscillating fan on the plants as it is, to keep the stems strong. However, someone also made a post on this site regarding building your own cooltube for the light, which is exactly what I'll be doing shortly.
This will allow you to get your lights closer to the plants. You could always buy a cooltube, but it would be more expensive and, hey, where's the fun in that?

3.) As for the car idea, I'm almost positive it will cause some harm to your plants. There are many things that could happen. Light leaks could cause a delay in flowering, your plants may go though some sort of a shock, etc.

4.) As for your problem of noisy eyes, I have never heard an eye make any sound, so I'm not sure how to help you. Just kidding. If you're talking about parents, the general rule is not to grow in your parent's house. If the police find your plants, the house could get taken away from them, and you may be removed from your parents. If it's a roommate-ish situation, keep a lock on the door. Do NOT tell them about the grow. Think of it this way, the more people who know, the more people who can bust your ass.

5.) There are many commercial products that will reduce the smell. I believe there is a debate over whether or not ionizers or o-zone generators can cause harm to your plants. Plus, it can't be guaranteed that this will eliminate the entire smell.

Good luck with your plants, and if anything I put in here is wrong or could be said in a better light, I would ask one of the more experienced growers to please do so, so we can all learn.