for issue #1 two steps ar required 

1. set up your  www.domain.com domain with a host entry pointing  at the ip of your dnn host you (this could take some hours to go into effect
2. add a new portal alias by login as host admin and using portals>add alias
3. optional you may want to remove the original alias when the new one is operational.

issue #2 is not dnn related - it is set up via host and alias entries in godady's the domain name server.

I just did the exact same thing yesterday.

This thread has my steps. http://www.dotnetnuke.com/Community/Forums/tabid/795/forumid/107/threadid/122581/scope/posts/Default.aspx

Everything is up and running.  The big key is to make sure you root has the correct rights.

If doing it again, the only change I'd make would be to add the new Portal Alias before moving.

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