Hi baby socks, there is a 17 month age gap between my 2 older girls, so i'll let you know my experiences.

How does a little one feel about having a baby in the house? I don't want to her to miss out on anything, get less attention and such.
My eldest, Jess, didn't seem to mind too much having the new baby at home. There were some jealousy issues at the start - which were usually evident when i was feeding Zoe. I just made sure that I was feeding somewhere where Jess could play, or i could give her cuddles at the same time. You just have to make sure that you schedule in some time just for your daughter.
How difficult is it to get them to sleep at the same times and such? Is it as much more work as I imagine it is?
I don't recall sleep time being a difficult time - but i guess it depends on what your sleep time routine is. If you need to rock them both to sleep , and they need to sleep at the same time then you may have some issues. I can recall giving Jess a couple of books, getting Zoe to sleep and then laying on the bed with Jess. You'll just work out something that keeps everyone happy when the time comes. You'd be amazed at how things just fall into place
Is it possible that the desire for number 2 so early on is caused by hormonal changes? I hated being pregnant, mostly because I was in a lot of pain, but now I miss it!
I'm not too sure about this one - but i know that i didn't have a strong desire to be pregnant with number two so early - so maybe it isn't hormonal. My dh really wanted a small age gap which is why we started trying so soon. .
Good luck