I'm adding an old Tivo HD at my other house

Although it's an old model, it's brand new and never has been activated/out of the original box. I know I have to connect it to the internet and let it add years worth of updates before I pair it with the Comcast card. My question is do I have to activate the Tivo before I can download the updates or can I get the updates and then activate the HD thru Tivo. I'm worried that the updates may take a couple of days and I'm concerned about how well the wireless adapter is going to work.

Is there anything else I'm not thinking about that I should plan for??

TIA