Don't make him hunt for the relevent reply:
The correct folder for replays would be:
c:\users\<username>\AppData\Local\Ironclad Games\Sins of a Solar Empire\Record-SinglePlayer
The "appdata" folder is a hidden folder, so you will need to change your windows settings to reveal it. You can do this from folder settings in your control panel.
Put the replay in that folder, then you can just watch it in game. Keep in mind that replays must be the same version of the game that you are running.
