How messy to get underlayment off of concrete floor?
Asbestos use in construction in the United States was banned in 1977 so there should be no asbestos in your house. To get the underlayment off, I would recommend using pouring adhesive remover available at any hardware store on the underlayment and using a sharp tool to get it off. Once you get the underlayment off, you can spread some sweeping compound on top of the floor and then use a broom to get the rest of the glue off. It is somewhat of a time consuming process but I do not believe that either of those materials are too toxic, and besides, they will be removed before putting down the new floor anyways.