Adding an Image into ActionScript: Newbie Question

Hello all,

I'm new to Flash's Actionscripting and I'm modifying a simple game
(Breakout) that was provided on the web by Flash. I am trying to
replace already defined sprites with an jpeg image of my choice into
an actionscript. (replace the bricks with a jpeg picture of my
own.)

After reading a book I bought from Borders (Essential ActionScript
3.0) and searching the web and trying different things, I'm a bit
fustrated. I thought replacing a sprite with a jpeg image would be
easy but apparently I just don't understand the event handling like I
should.

So, once creating an instance of my pictureURL and loading it with
Loader, how do I call it? I have a feeling I'm not understanding the
process of ActionScript events.

It says here that an event can be 2 things: built in and custom.
Built in events changes the state of runtime. My question is: when
do you know when to define an event listener? Do I need the event
listener? Is the listener needed for when the ball hits the
'bricks' (or jpeg picture) in my case.

I'm pretty confused, anyone with suggestions how I might go about
solving my problem is appreciated.

-m