Swap drives with exchange Roamio Plus?

Hi,

I have searched the forum for an answer to this question and did not see a definitive post on the topic, so am starting a specific thread. Please excuse me if I missed something in my search.

I have a dead (two year old) Roamio Plus (Box A). It will not power up at all (no lights on front, etc.), so I am assuming a bad power supply or system board.

I am expecting an advance exchange unit from Tivo tomorrow (Box B).

I am not particularly concerned about the shows stored on Box A, but my wife would love not to rebuild her extensive OnePass collection. The best answer I can get from Tivo is that the passes cannot be copied unless both boxes are up on the same network at the same time -- obviously an impossibility with a dead Box A.

Assuming the drive in Box A is OK, can I swap the drives in the two boxes? If so, is there an order in which I should do things?

If I cannot swap the drives, are there other options or suggestions to recover the OnePasses?

Thanks in advance for any assistance!