[JWait]

Look in skin/common_files/modules/One_Page_Checkout for the first one.
The default ".checkout-payments tr.payment-details td" is
is
.checkout-payments tr.payment-details td {
background: #ecf3f7;
margin: 0;
padding: 10px;
}
and div.address-book-link is
div.address-book-link {
height: 35px;
background: #ecf3f7;
width: 100%;
vertical-align: middle;
position: relative;
}
I don't know where the "none repeat scroll 0% 0%" part came from or what it does that has been added to yours.

To make the background transparent change background to
background: transparent; or background: transparent none;

Try each one to see if either works for you.