Actually, the headlight pieces are the easiest, and that's what I recommend to the beginners. The hood is easy to apply, but it is also very easy to get debris under it since it is a large piece. Also, it is very hard to get those debris out if they are located further from the edges.
So, I highly recommend start doing the headlights first.
Those side mirrors are the hardest because of many sharp curves, and then the front bumper is the next hard thing because it has many curves and just large (worst combination).