Dallas - thanks for the explanation.
One thing that would be a big help, is if you would email your users before making a major change such as this one. When I was an admin I'd email users saying "Hey, we are upgrading X this weekend, and we don't expect any problems but please let us know if you see anything amiss".
From the user's perspective this is very nice, because if X suddenly breaks, they don't waste their own time trying to troubleshoot it. Multiply that by the number of affected users, and you can see how a lot of time (and frustration) can be saved. It's very annoying when something breaks and you spend time trying to figure out why it broke, only to find out that it was A) a problem already known by the admins, or B) a planned upgrade that went awry, but in either case nobody bothered to tell you about it.