That is the shittiest of shit news and I wish you well however your story unfolds over the next few weeks, months and hopefully years.
Not sure if you want practical advice just yet but based on my own experience:
Start writing questions down as you think of them, it's really hard to remember things you wanted to ask when you're sat in the doctors office and information is coming at you thick and fast.
Make use of the Macmillan nurses, they really are generally excellent and will be a great help to you and your partner.
Share your thoughts and emotions with friends and family, you may want to put on a brave face in front of your daughter but with everyone else just be honest. This is no time for things to go unsaid.
If people offer to help, let them.
If you have any financial loose ends, try and find the time to sort those out. If you're entitled to any benefits during your treatment make sure to claim them. Although the financial side of things might sound largely insignificant under the circumstances I expect you'll want to be spending as much time as possible with your partner, daughter and family and anything you can do to alleviate money worries allows you to concentrate on more important things.