I would highly suggest that you hook-up the Tivo the suggested two days in advance. Run through Guided Setup (with either Analog Cable or OTA) and ensure that the Tivo is working properly. My first TivoHD would not go farther than the Tivo Animation screen. I ended up having to exchange it for a new one. If I had waited, I would have wasted a truck roll from Comcast. Also, you will to have the latest software update from Tivo before the CC are installed. There have been improvements in the software since the initial release, but the Tivo often still ship with older software releases. Finally, the downloads are fast, but nowhere near instantaneous. Plus even after the download is finished, the Tivo will spend at least 1/2 hour to 45 minutes, indexing the newly download data. You want to Tivo ready to go when the installer arrives, he is not going to wait for you run through setup.