I also have a 2008 Grand Prix, My fourth.
I buy the cheap engine degreaser from Wal-mart.
Get to the closest car wash so engine isn't so hot.
Spray the areas that need cleaning (no real grease on any of them), set the wand on rinse, and clear any soap from wand, then rinse down the same areas as above, low pressure and keep a distance, we're just rinsing here. I stay away from the electrical connections, coils and the alternator.
I do this once a year in the spring after the snow is gone for good. Car(s) have always started right up and I drive them a few miles to dry the underhood out.