Re: Change of domain name - same content....
Set up that domian in your control panel as an addon domain
Republish your old website to this new address making sure all the pages link together with the new domain name.
Remove the site from your old domain by removing the pages on the server.
Repoint your old domain to your new one in your control panel.
Reindex and market your new domain. Once Google have indexed it under the new name then use Google webmaster tools to have Google remove all old url's from the search results.
Don't aim for success if you want it; just do what you love and believe in, and it will come naturally.