Sorry, me again, I felt the need to comment further on your remark "the better mentally prepared I am....." I don't know how to explain this without sounding negative, but there really is no way in the world to be mentally prepared. I think if you can concentrate on that and realise that this is going to be difficult in ways you never imaged and that THAT IS OK, then you will have a head start. But being prepared is something else altogether.
I was SO FORTUNATE, jesus christ, so fortunate in that my Italian family hired a nurse to be on call for the first month. I initially thought that it was excessive and ridiculous. I ended up calling on this woman multiple times a day, even in the middle of the night and she always came within minutes. For simple and stupid things, but I could not deal. I simply was not able to manage the simplest of things.
BUT- READ THIS- I had many friends in the same boat, they absolutely could not even handle it but did not have the blessing of an on call nurse and they managed, they DID IT. They got through and both they and the baby survived. You can do this. But if there is any help available- people offering to bring meals, to watch the baby while you shower, anything, take it!
With my second child I refused the nurse. I said "I've got this, I know what it is like I've been through this before, I'm ok" Holy hell! It was the same mess all over again! i was sinking, dying, had no idea what to do. But I survived. My baby survived. It is possible.
I think what I want to say to you is to prepare for your sobriety more than anything else. Because the baby stuff is just going to be crazy and wonderful and scary and overwhelming and beautiful and whatever no matter the circumstances. The important thing here is to strengthen your sobriety so that you do not turn to alcohol or drugs as a way to escape. I would give my right arm to have back the moments I missed because I was drunk.