Need help with prep work
 

Hello Guys,
I am thinking about changing the color on my car and painting it myself. This will be my first paint job and want to do it right. The car was painted last year so everything looks pretty good. The paint does have a few small runs in it though. What would be the best way to start out sanding this car and will I need a primer coat to get started or can I paint over the paint that is on there now. What grit sandpaper to start and finish prior to paint. What is a good paint gun for beginners. I know that I have asked a lot of questions but any help would be greatly appreciated.

Chris