Just posting here because this is something that I'm personally struggling with as well.
I'm about a month and a half out from my D-Day, but 3 months out from when my WW voluntarily ended the A.
I have been blessed to have a coworker with whom I have been able to share all of this with. She had a marriage that was as bad as ours was up to and during my WW's affair. Talking with her to try and understand what was going through my WW's head has been instrumental in allowing me to cope and emphatize with the emotional state my WW was in leading up to and during all this. I'm not saying what she did was right. It wasn't, but I can at least understand how susceptible she was to temptation.
Anyways...that's a tangent. Two MC sessions ago was our first one dealing with the A. The MC said that my WW was to answer any questions I had, but that I also had to consider whether or not I was prepared to hear the answers and if the question really mattered to me.
The week leading up to that MC session I took a notebook and started writing down every question I had. I think I hit somewhere around 50 questions. Then I put the notebook down, talked with my coworker, and re-evaluated. By the end of the week I had cut that list in half. After our MC session...it was down to about 1/10 of what it was.
Now...the amount of information you'll want/need to know is different for everyone, but I would strongly encourage you to carefully consider how much information you really need...particularly if your WH is truly remorseful and you think it is true.
What I have found is that you can get borderline obsessive-compulsive about details that may seem like they matter at the time, but are really just your mind trying to comprehend what has happened.
Just like a lot of people here, I initially felt like I wanted to know everything: how many times, what positions, etc...
So I wrote those down. Then I thought about it and asked myself if knowing this information was really going to help me heal or if it was just going to make the pain worse. I know they had sex. I know it probably happened multiple times. I know it was in a hotel right down the road from our house. I've reached a point personally where I feel that's all I need to know.
For me, the most important questions were:
1. Why did you feel compelled to go outside the marriage to meet emotional needs that you weren't getting in our marriage?
2. How long did it go on and what did you tell yourself to justify what you did?
3. How did it end and why did it end?
4. Did you love him/her?
I've gotten answers to #2, #3, and #4. #1 is going to take awhile...honestly I don't even think she knows the answer right now. She says that it was a very confusing time...she was friends with a co-worker, they crossed the line, and she fell into the trap. Then began the seemingly endless cycle of something happening, guilt ensuing, then something happening again. My WW says she felt like it was her own private hell.
I would encourage you to focus on questions pertaining to your relationship with your spouse because ultimately that is what R is about. The OM/OW is just that and if they are out of the picture then don't bring them back in unless you need to.
That's just one person's opinion and I've got the benefit of a WW that is truly repentent and is holding herself 100% accountable for what she has done. I realize that I'm far luckier than other folks around here and I really sympathize with people having to deal with multiple Ddays, false R, and some of the other horror stories I read. I pray for you folks nightly.
Anyways, hope this helps. I also recommend reading After the Affair. There's an entire chapter on this issue. Haven't yet recommended it to my WW, but I think I'm going to at our next MC session.