Changing the headlight on the Impala is pretty easy, however the manual leaves out a couple of steps.  "Remove the air baffle."  Ok, what is the air baffle and how does one remove it?

Open the hood and the plastic piece between the grill and the radiator support is the air baffle.  There are three push in fasteners holding in the baffle.
These are the same type of fasteners we have seen before.  Gently pull up on the center and it will pop up.  When this happens, you can remove the fastener from the hole.  There are three fastners and the center one is smaller than the other two.
This is what the air deflector looks like when you remove it.  The top of the deflector in this photo is the front of the unit if you saw it installed in your car.  If you look at the top of the deflector there are two sets of three "fingers."  These tabs fit around the grill support.
The two outer tabs are below the support and the center one is above the support. Take a good look at this area before you remove the deflector from your car so you will know how to reinstall it.
These two white clips hold the headlamp assembly in.  This is the driver's side headlight.
The photo on the left is the clip when it is installed.  Pull up on the tab and it will move up about an inch.  This is a sudden movement so be prepared so you won't drop the clip.  The photo on the right is what the clip looks like.
Gently pull the headlamp assembly straight forward and it will come out.  Do not drop it!  The assembly is impact resistant, but you don't want to break it.  A new assembly is over $100.  The bulbs are behind the round dust caps.  Just lift them off like Tupperware lids.
This is the back of the turn signal bulb electrical connector with the dust cover removed.
You need to press down on this locking tab before trying to turn the connector counterclockwise to remove the bulb.
Lift the lock tab on the electrical connector and pull the connector away from the bulb's base.  Reverse the process to install the new bulb.  One note, do NOT touch the glass of the new bulb.  Oil on the glass can shorten the bulb's life.