Does anyone have any tips on how to get off the spring (push-on) nuts which retain the cables to the control levers? When I try to pull them up, they don't seem to want to come off, and the lever seems to move around, which I don't want to bend. Should I spray the post with a little PB blaster? Any suggestions would be appreciated. This is for a 1968 Cutlass S.

 

I use a pick to put behind them and push upward on the little 'teeth' that bite into the post. If they bend upward too much usually you can just press them flat again in a vice or pliers.

 

Those little push nuts are not considered to be reusable. You can get away with it if you're lucky, but don't plan on it - you might be disappointed.
You should be able to get replacements at a GOOD hardware store for a few cents apiece, but bring the old nut and stud to ensure a good fit.

Removal and destruction basically follow the same instructions (the result isn't clear until you're done):
Either use a small pick-like object, as CQR suggested, to push each point open and up, one at a time, over and over, until it's off (decent chance of saving the nut), or use a pair of ViseGrips or similar to grasp the nut and twist / wiggle / pull it off. At some point the nut will probably fold in half and suddenly become two pieces, but it will be off.

- Eric