I think what is important to healing is personal. It may mean that he gives enough details so you know he is not hiding things from you. Or so that you feel like you can trust him again. May be it is knowing how it started so you know it won't start again. May be it is knowing what OW's attractiveness is so you can work to improve yourself (though may be it does not matter). It's reaaly what is the most important stuff to YOU.
Then it is how much he is willing to give. Mine won't give me much details. (just had an argument about THAT!!!) Somehow there needs to be a balance between what he can give and what you can get. The rest, are you willing to live by not knowing? Also, it may take time. Granted if H is still feeling guilty towards OW, or may be not feeling 100% open to you, it may take a long time to get all the details.
This is a really hard part. i have no secrets that i cannot share with H. It feels really bad that he is keeping things from me. He claimed he is spending 100% of energy on me now. I told him if that's the case, don't contact OW!!! Somehow he cannot do that. I am waiting.....