ActionScript 3.0 :: Video Gallery - Adding Preloader And Setting MovieClip?

I am new to flashCS4 and done 2 of lee's tutorial's and have 2 questions.
1) how/where do I add a preloader to file when each vid is clicked on ?
2) how do I set a mc to be seen as a button in browser when you mouse over it ?
VideoGallery: [URL]

AS Code:
Select allstop();
hum1.addEventListener(MouseEvent.MOUSE_DOWN, vidStart1, false, 0, true);
hum2.addEventListener(MouseEvent.MOUSE_DOWN, vidStart2, false, 0, true);
hum3.addEventListener(MouseEvent.MOUSE_DOWN, vidStart3, false, 0, true);
hum4.addEventListener(MouseEvent.MOUSE_DOWN, vidStart4, false, 0, true);
[Code] .....