Well the Stormtrooper file says this:
Doesn't replace the original stormtrooper in /base folder.
So if you're wanting it replaced in SP, doesn't look like that's what it does. As for the other one, the replacement might not work on a saved game, if you're in SP. If that's the case, play through the level you're on and move on to the next one and it should work, OR reload the map you're on.