You need to either recreate or do the smart thing and extend the Web App. By Extending it you will allow it to be available on another url, where you can put it back on port 80. If you recreate it, just save the site collection via stsadm and restore it on the new Web Abb.
Central Admin -> App Management -> Create or Extend Web Application
Choose Extend and the existing web app, then give it a new URL & authorization method if needed
Option 2:stsadm -o backup -url "your url" -filename "somefile"
stsadm -o restore -url "new url" -filename "somefile"
as far as DNS goes, if the url is the machine name then no. If it is not the machine name then you need a host header and a dns entry to point to the static IP of the machine.