Ask HN: Resources for First Time Acquisitions

A friend has been tasked with orchestrating the merger between two similar (small, together bordering on mid-size) competitors. The actual terms of the deal have already been scoped out by the respective CEOs; what's left is really everything else. Are there any good resources or pieces of insight the HN community can offer for someone, and a company as a whole, going through this for the first time? I understand that this is an extremely broad question, but I guess specifically outside of general learning materials, things from your experience that went right or maybe more importantly terribly wrong would all be helpful, even if these may be different every time.

To be clear, this question is coming from the perspective of the acquirer, but perspective from the other side seems equally if not more valuable here.