Hi Treeseeds,
There's lots of great advice here in this thread, the only thing I can add is don't rush into anything.
You have a diagnosis and you may find in time that the diagnosis is all you need to deal with how you've been feeling. If you start making changes, you'll find that it's hard or impossible to go back if you should decide later that you desire to do so. This is true for both physical changes and social changes. You can't un-tell what you shared with friends and family. Remember a good therapist is going to help you figure out what you need to do, they should not be telling or directing you in any way. If you feel you are being push in a direction you're not ready for, consider looking for a new therapist.
Another reason to take you time is your wife and daughter. When you listed the "things that you are", you placed father and husband on the top if the list. This tells me that your daughter and wife are very important to you. Some will tell you, children are resilient, but the reality is that children do best with a mother and a father in the house. The greatest factor on how a child does in life is having a mother and father in the house. (The next two things are finishing high school and not having a child until they are married.) Give your daughter a father for as long as you can.
Next up is your wife. If your relationship with your wife is one where she won't flip out, but will give emotional support, please let her know early on. This however is not the norm. Most spouses will initially "loose it" over the news. If this is the case then don't share your diagnosis until you are sure you need to make a change. Then, as hard as it may be, do your best to get your wife on board before making any changes. You'll be better off in the long run.
Once you tell her, be prepared to give her the time she will need to "adjust". Be papered for large emotional swings as often this is the case. I really wish I could tell you your marriage will survive this; some do, some don't. I don't have any data on this, but from what I've observed, it seems that older couples tend to come out remaining as a couple more often.
There are lots of good resources here at Susan's, just take some time and look around. If you can't find what you're looking for, don't be afraid to ask questions. This is a very supportive and positive place.
I wish you all the best.
Paulie.