I would read the book before deciding whether to confront your W. I think you should maximize the amount of tools you can have to save your R before making any decisions or taking an action such as confronting her.
One of the first pieces of advice in the book is to stop have talks about your relationship and confronting your wife about an OM will likely lead to a relationship talk.
The book will give you a lot of ideas and techniques and the people here will help a lot, too.
