If you are in one of the 72.5 conversion markets, your receivers will not work anymore. That might be what the installer was referring to. If that's the case, you'll need one of DirecTV's newer receivers that are MPEG-4 compatible (bascially, one of the HD receviers).
How do I know if I'm in one of the 72.5 mkts?
I am in the Tulsa, Ok area.