AT&T U-verse technician coming to upgrade our wireless tomorrow - what questions should I ask?

We're upgrading our home wireless from 6 mbps to 24 mbps, and this requires the AT& U-verse technician to come install a new router.

We've been using the old AT&T router alongside an Apple Airport Time Capsule, and both routers are putting off their own networks. I wonder if they are interfering with each other as they have to sit right next to each other due to the ethernet connection required between them.

Any hints on how I can ask the right questions to get the AT&T technician to install the new router and set up the network in the best way possible? Thanks!