carefully removing shower surround

A couple years ago I paid a contractor to put in a bathroom in my basement. He did a poor job, many more problems than I'm going to get into here.
One issue is that, as far as I can tell he did not use nearly enough adhesive on the plastic shower walls. They buckle significantly as the shower warms up - to the point that one wall has developed a crack in it because of the buckling.
Do you think I have the problem diagnosed correctly, not enough adhesive was used? The wall is greenboard and I don't think water is getting back there.
If I understand the problem, then what I was thinking of doing was to pull the walls down, clean things up, and re-install.
1. How do I easily remove the plastic wall without damaging the wall or greenboard? Some solvents? I'm worried about just pulling. Not sure what adhesive he used. 2. What type of adhesive do you recommend? 3. How much and where exactly do I apply new adhesive to prevent buckling? I am hoping that a little extra adhesive on the back side of the short crack will prevent it from expanding or allowing water through. Doesn't have to look perfect, it's a 2nd bathroom in a home we will be selling in a year.
Thanks. Brian

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