Dans. You are acting so quickly. Are you absolutely sure a 28 year old marriage should be thrown away after one mistake? Are YOU so perfect? Why did your wife come to you with her terrible secret? Was she trying to get rid of her guilt, or was she trying to tell you there was a problem she wanted to find and fix?
And if you are sure you want it to be over, if you really can never value marriage with her again, please slow down. Take your time. See how easy or difficult it is to get yourself settled, and make sure you won't actually need some of those assets you want to sign away willy-nilly. Listen to your attorney. Let the professional fully advise you of your rights and responsibilities before you go off signing things.
To answer your question, I stayed with a cheater for almost a year after I found out. I had much less time invested in him (five years) and he had been fucking pretty much anything which moved. Initially, I did want to just break it off, and that's what I did. He fought very hard to keep me, and eventually talked me into seeing our pastor for counseling. Pastor talked us through some things, and convinced me to take him back. Over the course of that final year, I was a lot less trusting, and more jealous. But only inwardly. I was careful not to treat him like a criminal. Still, we just couldn't hold it together. I sensed he wanted to fuck other women, and wasn't sure if I was right or not, but, as you fearfully projected, I didn't want to be the jealous girlfriend anymore. We mutually agreed to stop trying. Then he kept trying for a few years, but I tried to move on.
I do not regret staying. I'll never have to wonder if I had casually tossed out something that had been so precious and delightful for so long. I'll never have to wonder about what might have been. Personally, I prefer to live a life without regret. After five years, I was willing to try for about one year. After 28 years, I might be willing to try for a bit longer than that, or a lot longer than that. At a minimum, I know for a fact I would seek outside help first. Guaranteed.