My grandfather was there, and he didn't paint a very pretty picture. Imagine a guy you've trained side by side with for months, and fought with get his brains blown all over you. Yah that would have been fun (Note the sarcasm). I wouldn't have liked it, and I don't know if I would have volunteered. I say yes, but the only way one can know what they would do in a circumstance like that is to have it come up and kick them in the ass.
As for selection, If you happened to be in a regiment selected by the SAC, then you went. The Royal Canadian Regiment was the first infantry on the beach to give them a chance at payback for Dieppe. Other than that regiments were chosen based on experience (except for the Americans who at this point had none), availibility (regiments which could be assembled to the staging grounds the quickest were the first to go), and capability (training added with the amount and kind of hardware availible).
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Remember Dieppe
