[SOLVED] Different background per page id

I have been reading through the threads and the closest I could come to a solution was something in the lines of:

Part 1:

<div id="imagecontainer" class="header-image-container"></div>


Part 2:

div imageContainer # {
background-position: top center;
background-repeat: no-repeat;
background-image: url (/wp-content/themes/atahualpa342/images/home-bg.jpg)
}

body.page-id-3 div imageContainer # {
background-position: top center;
background-repeat: no-repeat;
background-image: url (/wp-content/themes/Atahualpa/images/home-bg2.jpg);
}

What I want to do is NOT replace the header, I am using the header. I am just also trying to assign a different background image to a different page id.

Is the above code correct and if so, into which sections do I put it, because I have put Part 2 into CSS INSERTS, but I am not sure where Part 1 should go and if this is at all correct.

Help would be appreciated. Tx