Both my wife and myself have had the Smith message but have had no impact on functionality, as have many others here and on the Sprint forum. We have been able to just swipe the message away and it stays gone until next restart.
Have you taken the extreme measure of doing a factory reset on your phone? This is a PITA, but could be a possible fix, and you may have an unrelated problem that presented at the same time as the expiration of the Smith application. When all else fails, start over from scratch.