I'm no expert... But I have it working with Google Checkout. I used "WinMerge" (A free and great tool- wish I'd had it years ago) and merged the file together. Using the file with Google checkout already in it and added the COWOA code to it. I think (and like I said, I'm no expert) that you really have to worry about:
includes/templates/YOURTEMP/templates/tpl_login_default.php and
include/templates/YOURTEMP/templates/tpl_checkout_payment_default.php
Nancy




