Guys you are best to call DishStore and ask for Claude, or tell them you want to signup for DirecTV and they'll get you some help.
(800) 807-0837
To my knowledge they do new signups for DirecTV. I don't think at this point they are straight selling receivers for existing accounts, though I could be wrong.
Most installs are completed by DirecTV's HSP network, just like if you ordered from 800-Directv or directv.com.
Installers generally use whatever hardware is availalble, but if you order the whole-home DVR you are near-guaranteed to get HR24 equipment. Most of the time installers have older equipment it is used for service calls etc. New installs almost always get the newest stuff.