Guides
Three things worth knowing before a system gets replaced here.
In Kentucky the credential belongs to a person rather than to a logo, so the licensing guide is ten minutes well spent ahead of any of this. After that it splits by what you have in hand: equipment that is old but still running is a lifespan question, while two numbers that disagree are a pricing question. The two are easy to confuse, and confusing them is how a working system gets retired early.