"What would happen if I cheated on my wife?" - you'd be a lowlife, scumbag, selfish, morally-deficient cheater (that is, if you aren't already).
"Will she find out for sure, guaranteed?" - Maybe. Maybe not. Nobody here can see the future, dear.
"The first time?" - Plenty of people get 'found out' their first time slumming. Some don't.
"Will she give me another chance, or divorce me and take me to the cleaners?" - Again, nobody here can see the future, dear. She may give you another chance (not if she's smart though), or she may divorce you. Nobody gets 'taken to the cleaners'. Your cheating wouldn't affect the outcome of your divorce or the asset/debt division. It would only affect your karma. What goes around, comes around.