I don't think I've ever met a person who went down the road you're thinking of traveling -- and was glad afterward that they did so. I can guarantee you won't be the exception. The Bible says, "Can a man scoop fire into his lap without his clothes being burned?.... So is he who sleeps with another man's wife" (Proverbs 6:27,29).
My advice first of all would be to cut yourself off completely from this situation -- even if it means changing jobs. At a minimum, break off your contact with this person -- and perhaps tell her why, so she knows you're serious. Don't assume you can back away "just a little bit" and still keep temptation at bay; it probably won't happen. Paul told his young pastor friend Timothy to "Flee the evil desires of youth" (2 Timothy 2:22).
But second, I urge you to do everything you possibly can to strengthen your own marriage. God gave your wife and your family to you; don't turn your back on His good gifts. Spend time together; listen to each other; be patient with your spouse; express your appreciation for her. Marriages usually don't suddenly collapse; instead, they just drift apart. Make it your goal to restore your marriage -- and you can, with God's help.
Most of all, turn your life over to Jesus Christ. Right now, you're fencing Him out (so to speak); break down the fence and let Him in. You'll never regret it.