I would start by unplugging the HD receiver for several hours. Also you might want to move the SD receiver in where the HD receiver was to see if it's the wiring. If the HD receiver still fails after being unplugged for a while then you're right, it may need to be replaced.
Computer updates at DIRECTV don't take very long so you'll probably be ok should you need to call again.
Computer updates at DIRECTV don't take very long so you'll probably be ok should you need to call again.