That's actually the part that I was getting confused by. Does everything with a yellow caution sign have to be upgraded together, or can that happen over time?

Reading it again, I'm assuming they're overtime and individual upgrades that can take place? If someone could confirm or deny that for me, I would appreciate it. I may just be overthinking this table.

Edit: yeah that's what I'm taking away after rereading this a few more times. Very impressed by the modularity on each of those parts.