I just tackled this on my '69. I've had the new cigarette lighter bezel for 8 years but never figured out (or took the time to) how to replace it.

Today I finally did it! As mentioned above, it needs to unscrew from behind the dash. It is accessible without taking the cluster off, you just need to crawl underneath on your back. Also mine was rusted on good, so I used some PB Blaster soaking for 30 min. to loosen it. After that was able to unscrew it by hand, no tools needed.