I never did much with PC's. Large-scale mainframe systems was my bread and butter. With upgrades (sw and/or hw) we always did a test run on a backup system first. If everything worked properly then the actual upgrade was scheduled during whatever window the customer set. On that day if it didn't go well we had to be back up and running on the old sw or hw at the planned time.
Those upgrades always involved a lot of people on the customer side to verify everything was properly working.
Our biggest supplier at work changed over to a new system about a year ago and it's just now starting to straighten out. It has been a nightmare ordering and receiving orders from them due to that and then put the supply shortage on top of that. I don't know why they didn't revert back to the old system once they saw how messed up the new one was. At one point they had us on credit hold due to stuff that we ordered that they had on backorder to us. We had placed an extra 200k order to stock up on some machines we sell a lot of and they were on backorder but showed on our account. We had to call and see why our orders weren't shipping and they unlocked our account.
