Start up one system at a time and test it. Make sure it works before your customers have the opportunity to find out. Once you have established a system is operational, move to next system. If a system is not fully tested and Y2K ready, take it offline until it is ready. It may be better to have a server offline for a temporary period than to have it fail during a critical time, harming customers, and taking other systems down with it.
Contingency planning can make it feel like the sky is falling.
View these simply as good, prudent actions you might take to protect your investment. Two final thoughts. First, stickers are always fun. One trick is to stick one color sticker on every piece of equipment that has been inventoried, and then another color sticker on every piece of equipment that has passed your scrutiny. Second, consider the financial impact.