I've done this by adding a shopping cart pane:

function yourmodule_cart_pane($items) {

$panes[] = array(
'id' => 'your_id',
'title' => t('Title'),
'enabled' => TRUE,
'weight' => 10,
'body' => 'YOUR TEXT HERE',
);

return $panes;
}

In my case, I used the $items variable to see what was in the shopping cart and suggest some other products the customer might want by inserting a view.

Hope that helps,
Xerxes

I haven't done that yet, but it looks similar:

http://www.ubercart.org/docs/api/hook_checkout_pane

I assume you would just have the callback function return the text you want displayed.

Where exactly does this code go? I tried putting it in uc_cart.module below where the original cart pane code is, and it just broke. Of course, I could have formatted it incorrectly.