All licenses open, all cars (plus bonus cars), player rank 1st, $72 million cash, all cheat codes unlocked. Extract to your My Documents\Codemasters\GRID folder. Make a backup of your existing savegame folder before overwriting. You may need to edit your profile to reflect the current country in the game.
Trainer options are activated using the NUMPAD on the right side of the keyboard. You will need NUMLOCK 'On' for the hotkeys to works properly. Laptop users may need to plug in a USB keyboard to get these keys.