Rich - don't get too overheated on "exposing directly to the Internet" LMCE. Of course you don't have to do that if you prefer to have another firewall in between. But don't forget it is far from directly exposed anyway. It will be behind your DSL/cable modem on a private IP range. Even the most basic broadband router will provide more than adequate protection as long as you aren't NATing a whole load of stuff. Seriously, this is a non-issue.
Picking up some other points - you don't need to "get SAMBA working" on this system, it is there by default and running - nothing whatsoever to do.
On NICs, yes its perfectly possible to set it up with a single NIC. But why bother, save yourself the aggravation, arguments and compromises on the configuration - for the sake of a component you can pick up for less than 20 bucks these days, again its a non-issue, just go with 2 NICs.
