I just finished up my first book and while it is much shorter than yours will be (18k words) I'll share what helped me:
1. Write how you want to write. In other words write in your own style. If you are funny, that's fantastic, but if you prefer to present things in a straight-forward methodical fashion then do that. You will be spending a ton of time writing and re-writing: It will come much easier if it is in your own voice.
2. Don't be afraid to jump around. You do not need to start writing with chapter 1, then on to chapter 2, etc. Write whatever you are inspired to write at the moment. You can always go back and fill in the hard stuff later. You should do everything you can to make the process enjoyable, so, with that in mind, procrastinating frustrating parts is OK.
3. Write on a schedule and stick to it. If you don't feel like writing but it is the time you've scheduled, do it. I found on a number of occasions that even if I didn't feel like writing, once I started my mood shifted. Although sometimes I just failed to produce anything.
That's just off the top of my head. I'll come back and add more if I can think of worthwhile stuff to add. I will say though that the act of writing and completing a book was tremendously empowering and fun.