Apache gurus! Question....
 

When you add a virtual site is the only file that is updated the httpd.conf file?

No, you must go to resolv.conf as well and setup your DNS.
EDIT: Files affected are httpd.conf resolv.conf and a new file will be created called yourvirtualhost.domain.tld.db on /var/ or /var/hosts or anything as default by your system.

uh..ok. sure.

if the question is: what do i have to do to add a new domain to apache: edit httpd.conf and feed it a graceful restart. This assumes your DNS is already setup correctly to resolve your domain name back to your host.

If the question is: what files get touched: lots. You shouldn't care.

DNS is running on another box. so i guess httpd.conf would be the only file?

That is correct. For most apache configuration, that is the only file ever updated.

Interesting indeed....