For a really thorough guide to DNS, there's already a few really good resources out there;
If you're into books (the dead-tree kind), I *highly* recommend getting O'reilly's "DNS & BIND
The Internet Software Consortium maintains a great Administrator's Reference Manual
for DNS, too - They have one for each major release of their DNS software (which is found in most Linux distributions).
Keep in mind that with /etc/hosts, there's no "MX" equivalent. You'll almost certainly have to setup a DNS service on your network. In fact, I would recommend that you setup two systems with DNS, and have one be the master.
If you *really* want an exercise in Linux, read up on some of the virtualization software available for Linux (*cough* Xen *cough*). Then setup two virtual systems to host your DNS.