Someone here, as well, who's been through it and come out on the other side. It's taken a couple of years and more tears and arguments and midnight-to-4AM talks than I can count...but, honestly, our relationship is more beautiful and we love each other more today than we ever did before 'the situation'. It's hard, and your heart will probably break a million times before it's over, but just know that God can and will heal what's been broken and make it stronger if you just let Him.
We never went to counseling, though we probably should have. Truly, it's only by the grace of God that our marriage survived. But I'm so thankful that neither of us threw in the towel...even though we both thought about it at one time or another.
It's something that your wife confessed to you with a repentent heart. She sounds as though she sincerely wants to make things right. Everytime you're in doubt, just say a prayer. Pray that your wife be freed from the temptation or weakness that caused her to sin, and also pray that God would open your heart to your wife and give you the strength and the peace to forgive her. You have to forgive her for there to ever be a chance. You might never forget it completely, but if you truly and sincerely forgive her, then there WILL be a time when it doesn't hurt you to think about it.
Honestly, when I look back on it now, my husband and I both were completely different people. Looking back is almost like watching a story about another couple. Neither of us will forget it, but we've moved way past it.
BTW, we've been married a little over 7 years...this happened around the 3rd or 4th year, I guess.
Welcome to CF.