Getting wireless

Hey y'all, I'm coming back to U-verse after a couple of years with DirecTV.

The install should be fairly straightforward (all my existing CAT-5 wiring is there). However, I will be putting a TV in a different room that doesn't have a CAT-5 drop and the coax drop on that room is in a lousy spot. I would like to get a wireless receiver in that room.

When I placed the order online, there wasn't any way to request one. The website says to ask the installer. Should I assume that every installer has them on the truck? Or would I be better off calling and asking for one prior to the install?