Can you clarify which light assembly you are trying to replace or post a picture of it?
Perfect! that was easy!
The rear panel has to be removed. There is just one bolt that hold the strap on then the panel needs worked off. Use some protective screw driver ends to pop the panel loose the work your way around. Then there are just the 4 nuts that hold the light in. Click the links below and save the pictures. This will clear things up. If you need anything else let me know.
P.S. I take great pride in providing quality responses for the people I assist. If you believe that I have been professional and helpful in my assistance please don't forget to give a positive rating for this exchange and click the accept button. If you feel my answer does not address your issues, please just tell me and I will opt out, allowing another technician to address your situation. My Goal is to make this experience one you appreciate.