Exchange Topology - Astaro Config

Hi, i am going to be installing my very first exchange server shortly and just wanted some advice on implementation in an Astaro network.

Question 1: We are a small business and will have around 30 mailboxes. I am assuming that I do not need to setup edge servers etc, I should be good with just the one server hosting all exchange services?

Question 2: If I only need the one server, where should the Exchange server sit? Does it need a DMZ?

Question 3: Is there a good tutorial on setting up Astaro to securely accept incoming and outgoing mail along with OWA?

Thanks in advance, sorry that these might sound like noob questions but this is my first with setting this up :)