You have to remember, GM did not intend these things to last 50 years, so the design may leave a little to be desired
I know John suggested the same thing when I had problems with the sending unit on my Post Sedan. I could not get that push nut thing off to save my soul, it just dug in more when I tried to remove it. With all the fragile components on that sending unit, I figured I was going to end up doing more harm than good, so I just sent it off to John Wolf & Co. in Willoughby OH and they fixed it up good as new. I am now having the same issue with my convertible, so I might try this again when I get around to fixing it.