AT&T U-verse → U-verse and Airport Extreme

I'm scheduled to have U-verse installed tomorrow. I was told I would be getting a new business class Modem/Router. I already have an Airport Extreme and am very satisfied with it's performance. Can U still use my Airport Extreme with the new modem/router?

Yes, you can.
You need to put it in the U-Verse RG DMZ-plus.
1) Connect your apple airport to one of the ports of the U-Verse RG and power it on
2) Connect your computer to the RG with an ethernet cable or its wireless network and login to the RG (default is 192.168.1.254).
3) Click on Settings
4) Click on Firewall
5) Click on Applications, Pinholes and DMZ
6) Select the Apple airport device in option "1) Select a computer"
7) Under option "2) Edit firewall settings for this computer", select "Allow all applications (DMZplus mode)"
8) Dont forget to click the save button at the end of the page.

I would also disable the wireless on the RG and only use the wireless on the Airport Extreme.

Alternatively just connect an Ethernet port on the 2 Wire to the Ethernet LAN port (labeled "<->") on the AirPort and in the Network tab of AirPort Utility, set the Router Mode to "Off (Bridge Mode.)"

Well by this date you should already be up and running.

I connected my AE (Wan Port) to one of the RG (Lan Ports) I also put my AE in bridge mode. I also turned off the RG wireless function. This has worked well for my needs for 2 years.