Paint Sprayers, What to look for when buying?

I am searching for information on paint sprayers and painting autos. I used to do alot of painting with my dad years ago,using his setup, As he was always building race cars.

Dad's not around anymore to ask, So I thought I would throw the question this way.

We had to buy a new compressor the other day, And Im sure it's suffecient to use a sprayer with.

What do I need to look at when picking out a good one?

Gravity fed, vs. the tube type?
Flow rate on nozzle?
Metal or plastic?
Any advice would be appreciated.

Also, I wonder what is neccesary to prepare a car with clearcoat on it before painting?

We have a 95 Honda,and a 99 Saturn we are putting body kits on,

We would like to paint entire cars, and change the color from gold to blue on one, and gold to red on the other,
and I dont think any of the old cars we ever painted had clear coats...LOL

Do you sand them completly down, Then prime and paint? Or can you sand them smoothe,Then paint?
How many coats are clear are suffecient to protect the paint?

I would apreciate any knowledge you could share on auto painting?

Of course, I am a bit rusty I'm sure, but we have a 90 mazda no one drives I can practice on, as well as a few other things to get back in the flow of things before I lay it on our project cars :-)