I've added the menu on the checkout page and added the server behavior on the confirm page. I'm not sure how to configure the trigger.
In your post you said:
Once you have both of them on the confirm page you can them update the triggers to look at the posted value for the shipping selection that comes from the checkout page. If it is one value you would use UPS, and if it is the other value you would use USPS.
How do I pass the value "UPS" or "USPS" to the confirm page? My menu uses the select name and id of "shipping_type" and it shows up in the "ecart_checkout_form" on the checkout page in the bindings panel, but "shipping_type" doesn't show up as an option in the confirm pages binding panel.