I had similar thoughts. I'd like to connect my system to the internet, but it's not worth $100 to me.
I was able to get my dvr connected to the internet by unplugging the dvr and dsl modem, then connecting the two, and then power both back up. Then I let the ran though the dvr setup menu and it connected automatically. On the down side this took away the multi room dvr viewing.
From what I've read, the whole-home dvr uses your coax to connect your receivers. Once you connect the dvr to the internet, it wants to change over to your homes internet network. So if you connect 1 to the internet, you will need to connect them all to that network.
I'm not sure how the professional installer makes that connection. Maybe he installs something that allows for that network to run through the homes coax?