Help with body HTML for background layering

HI!

The template I chose to alter for my blog is turning out to be a bit beyond my greenhorn ability. I would appreciate some assistance in getting a background image behind the following code:

body {
background:url(images/page-back.jpg) no-repeat top center #000000;
margin:0;
font-family: Tahoma, Arial, Helvetica, sans-serif;

The above code controls the main notebook graphic and various smaller graphics, and attached to it is a colour code that I have changed to black.

I want to add an additional background image to match the rest of my site. My desired background image file is this: background: url(images/heritage-scrap_background.gif);

I have tried just replacing the original code with the line above – and it wipes out the graphic image and formatting of the template.

Is there a way to have my desired background image layer underneath the original body code? That way it would not affect the template?

My blog address is http://www.heritagescrap.com/blog

You expertise is most appreciated.

Kind regards,
Kate