I currently have a couple of SD DVR's. I would like to have a HD DVR. Can I buy a used one from ebay and simply insert my access card? Does it matter if the unit I get is leased or owned? I read one guy selling a least unit contacted DT and they said they don't want it back... can I use such a unit by inserting my access card? Finally what model number should I get? This is confusing and I appreciate your help.