You definitely should setup an external web server instead of the one that comes pre-installed.   Apache or IIS on the same server would be fine for size you describe.   Anything you do with webservices/SOAP/ITK messaging as well as FHIR should be done on an 'external' web server rather then the built in one.   I'd also recommend setting up SSL from day one.   Both of these things are rather easy to do now but more challenging to change down the road.

The built in web server is great for local development but is too limited in it's configuration for use on any sort of live server, sooner or later you'll run into problems, might as well take a couple hours now and do it right.

-Matthew