The tech from ATT will do it. Just make sure that the person who handles all of the technical stuff in the household is the one there. My neighbor has her RG sitting on top of her desktop, which sits next to her computer. From there, since she got TV, they placed a phone jack for the telephone feed of Cat-5e for the RG to receive a connection, and just plugged into the phone jack that was already there, so her phones in the house would have service. Time wise, it depends on how old the drop from the pole or box to your home, and how bad the inside wiring is for the telephone, if any odd changes were made earlier, and they have to clean it up.
Just remember, you are in control, and if you do not feel comfortable, stop them before they start any work. I spent five minutes visiting with my tech before we started, by walking through the home, and showing our current setup for the network, and where I have my LAN set up downstairs for distribution, and placement of the equipment. Tech's love me, since I have a easy clean set up, and everything is cat-5e, already wired.
Tonight, just go through surveying your setup that you have already, and look at where the telephone enters your home or apartment, so you get an idea of the scope of work. Also, go to http://www.uverserealtime.com and download the tool, since it will help if you have any problems with your service, and also can allow for monitoring of usage. Post back if you have any questions tomorrow.