In my option:
- Depending on what kernel version and Storage you have on a 6200 this can influence the time to install/boot.
- I would generally say between 10 - 15 total time just for the unpacking, installing and reboot, personally I prefer to uninstall the old jumbo first, then install the new one so double the time.
Clearly you need to do this in a maintenance window, and of course snapshot, as Magnus is also correct on, allow for worse case scenario, you need to restore the snapshot, this can take between 30 - 45mins as an estimate.
Of course something else that is good it have is a LOM card or out of band access.