hm... no way you can get a game like that in one month and with a budget of $1000 and i also don't think it could be easily done with 3dgs.
city full of cars (with realistic physics), day and night mode, weather, pedestrians, car ai, split screen mode, 8 player network mode, easy to use level editor, farm land level with farmers, sheep, cows, barns and much much more... sounds a bit like san andreas to me.