First of all congratulations! You're in for a fantastic adventure!
I have a 22 month old boxer baby boy named Riley and an 8 month old human baby boy named Declan. They are already becoming great friends and it is wonderful to see them interact.
We did prepare the nursery well in advance, at least a month ahead of time, and let Riley in to explore and sniff things but taught him that the things in there were NOT his toys. We only let him go in there when we were in there with him. Otherwise we kept a baby gate across the door (he knocked over the baby gate once and it scares the dickens out of him so now he won't even go near them!).
I think Riley was aware that something was up with me because he did become much more vocal and protective during my pregnancy. Not sure if that was just a maturity thing or if he "knew" he would have a new role as protector.
We also had to go out and buy a nice plushy bed for Riley, because he was sleeping in our bed with us, and I thought that would be a less-than-ideal arrangement for nighttime feedings (whenever I got out of bed to pee, which was often,
when I was pregnant, I'd come back to find that Riley had stolen my spot!!). Anyway, we made the transition to his own bed about a month before too.
When Declan was born, my husband brought home the little knit cap they put on his head when he "first came out". It was kind of icky with stains on it, so we figured Riley would get a good idea of "scent". Riley was able to sniff and sniff and sniff it and he was told all about his new "baby brother."
When we brought Declan home, I went into the house first, by myself, and greeted Riley. He was so excited to see me since I hadn't been there in a couple days. After a few minutes my husband brought in the baby, and we allowed Riley to sniff at him a bit before baby and I retired to our room for a nap!
Guests that came to see the baby knew to give Riley some love too! It really is like having another child. I've read/heard that you need to consider a dog like a 2-year old around the baby. They can only understand so much of what you're telling them to do/not do, and you would never leave a 2 year old unattended with an infant.
Riley has really been terrific during this whole new "adventure" for all of us. He's still our baby.
Sorry so long! Hope it is somewhat helpful or encouraging. Good luck again!
Courtney
PS. One thing you may find VERY helpful is a Baby Bjorn frontpack carrier. I found it SO much easier to walk Riley with the baby in that rather than trying to juggle a stroller and leash. I still use it now, even though Riley is quite used to the stroller too. The only thing it makes tricky is the poop pick-up! ;-)