I would like to update the existing Apache software to version 2.2.22 (currently running version 2.2.21). I would like to use Macports but I am open to suggestions. Whenever I try to install it, MacPorts defaults to the /opt/local directory so it installs a second instance of Apache without updating the currently installed version.
From your comment asking whether you could disable the existing installation, I don't see why this shouldn't work:
Then you could manage Apache from the MacPorts version. It wouldn't be through the UI though, but as long as you start the service, it should work just fine.