The entire 1000 points from this game will come from simply beginning a game on Hard and playing through the campaign. Once you complete all nine chapters on Hard you will be done. There is a small trick you can use to beat the game on Easy, then only have to replay the final level on Hard and get credit for the "Seasoned/Veteran Commander" achievements. I didn't really find the game all that difficult, but there were a few frustrating parts. The trick can be found in detail here if you need it. Otherwise, play on Hard and use the videos from this Mahalo walkthrough if you get stuck at all.