My first Tivo was a Series 2, which I am still using. My second Tivo was a Toshiba SD400 that recently died. Later this week I am going to pick up an HD to replace the dead Toshiba. I am still paying for both of my old units with the dead Toshiba as the second unit at $6.95. How much trouble am I going to have switching the subscription from the dead Toshiba unit to the HD? What is the process?