^Depends on if you want a complete playthrough. If not then there's quite a few corners you can cut. Just be sure you have at least two loyal teamates by the end of the suicide mission.
I'm hoping to do a fairly complete one. Though I may try to get Miranda & Mordin killed, now that I think about it.
Also, a word of warning for anybody doing this: uninstall Arrival. Or else the intro cutscene will trigger as soon as you finish Horizon and try to use your terminal.