Hey Mitch,
The DNs need to go to 3 digits anytime an expansion card is added to a system. The reason is, all possible DNs are available in software, for all equipped expansion ports on the system.
The DN length on the StarTalk Mini will need to change as well. This will involve a reinstall of the system.
Yes, you will have to power down the system to install the expansion card. Will you loose any programming? No way to tell. I get nervous anytime I have to power down an 824, because they are so old that the NVRAM is close to being shot, if it isn't already (unless it has already been replaced). I would make sure to document all of the system programming, just in case you have to rebuild it.
Good Luck!
(Shoot me an email if you need the reinstall process for your mail.)
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BCM Guy
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