prep work, before painting Options

[jayi12-15psi]

I'm about to have my car painted and I would like to save a little cash by doing the prep work by myself. Is there a good place online to read a "how to" on prep work? I've never done to much body work, I've worked a little on fiberglass but nothing to big. My knowledge as of right now consists of:

Sanding the original paint down to the primer using 400 grit, do I just use regular sand paper for this? should I start with a lower grit and work my way up? Should I just use an electric palm sander? Also What is a "wet sand" I read it discussed in another thread.

I plan on taking all the trim off of it except the windows.

is there some kind of paint stripper I should use? Do I put on another coat of primer when I sand down to the stock primer?

Sorry for all the questions, thanks for reading.

[Drocay]

2000 is way to fine, but i used a 400 wet sand from 3M. power sander isn't needed just a block.