Hi jft69z,
I managed to get the driver side headlight bulb replaced today, except it took nearly three hours.
The metal and plastic retainer as pictured in the diagram labeled as #2 and #3 were blocking the headlight from moving. The driver side headlight seemed to be positioned a little higher than the passenger side. I was able to pull it out just enough to where the square blocks rested outside the retainers on the passenger side, but the driver side was restricted.
There is also a little plastic notch that is located behind the headlight that slid out of its hole and allowed me to get another inch of work room. I believe that is pictured as #4 in your diagram. Even with this notch out of its place, it was still difficult since the headlight was still stuck inside the retainer. If I tried to reposition the headlight and line up the square blocks rested outside the retainer then this notch would slide back into place.
Here is the amount of workroom I had with the notch behind the headlight pictured above out of its hole. I had to forcibly remove the dust cap by bending it tightly. It worked, but when placing it back in it was another ordeal.
This is what is underneath the cover after removing the plastic rivet circled in red. Underneath this plastic cover were more plastic rivets, but these had a flat face and were much thinner. I could not grip them with pliers like I could with the one circled. These are some images that I found online from someone who managed to do it on a 2008.
The green dots are the rubber bumper plugs that I originally mentioned. To get access to it, one must remove the 4 plastic retainers labeled as the red dots with the flat face as previously mentioned, and move the grille forward a little to have more working room. From what I can tell, there wouldn't be a need to remove them (they DO NOT budge at all), as you can slide the plastic piece it is holding upwards and out.
Here is a very clear walkthrough of how to replace the headlight bulb:
http://www.fixya.com/cars/t6770306-change
I found that link after an hour of frustration trying to move the headlight, so I followed their steps but to no avail since I got stuck on the rivets that I could not remove. If someone is able to remove those plastic rivets holding the grille in place underneath the cover, then there should be enough room. As far as removing the headlight? I am not sure.
There has to be an easier way than this though. Needless to say, I do not look forward to replacing my headlights. I am a bit confused with what it means by
"Loosen either the LF or RF bumper fascia corner in order to flex the fascia when removing the headlamp assembly." Would you happen to have access to the 08-09 LaCrosse service manuals?
Thanks!