Two different answers, both vague. Most of us made the change years and years ago and have no clue where/how to "rename the admin folder" or how to "re-upload from the client area", let alone exactly how to modify a config file (or where to even find it).
This is all cryptic gibberish.
Since IP is forcing this change to non-tech folks, I highly encourage IP to create very explicit, step-by-step instructions for dummies so we don't flood these support forums for help when the change takes effect.