you can not.

just think about it: 80 to 100 years uptime, no reboot, no fall back system, not even a cold spare. and you want to change something while its running? madness! maybe if you are very lucky you may be able to replace some of the internal components… but not to upgrade, only if your on the risk to loose the whole system…

Never change a running system. Even small changes may have unexpected consequences, if the machine is as complex as our bodies…