I swear y’all are making this way harder than it needs to be. Any time you want a receiver to be replaced, buy an HDDVR (HR20 - HR24) or HD receiver (H20 - H25) with access card on eBay or similar website. Without the card, you would be asking for trouble.
Once the receiver arrives, use live chat with any agent and ask for receiver activation. Give them the receiver ID, access card, serial number, and model number. If they ask about the receiver, claim it was an additional receiver and not a replacement. Make sure to say that DIRECTV sent you the box. After a few minutes, they activate it.