eCart with UPS using real-time shipping quotes

I have been using eCart for some time now but have always created my own shipping lookup tables and have calculated shipping costs based on weight ranges. Now, one of my clients is interested in possibly using UPS and utilizing real-time shipping quotes. I have two questions.

1. They are potentially going to be shipping some very large items and were wondering, if they used real-time shipping quotes, if they could somehow override certain products' shipping charges and have those calculated separately? I couldn't find any documentation on such a scenario as this.

2. Is there some documentation that would indicate to me WHERE in the checkout process these shipping charges would actually show up on screen for the customers? Am I correct in assuming that the client would NOT see shipping charges calculated while they were adding items to the cart, and would only see the shipping charges after the API call and those charges would appear on their final checkout page?

Can someone shed some light on this so I know how to advise my client in moving ahead with their project?

Thank you :)