You'll need to do a 301 redirect or else you'll go into duplicate content hell. Fortunately this is not difficult to do. You'll need to add the following lines of code to a file called .htaccess and place it in the root directory of the website:
Code:
RewriteEngine On
RewriteCond %{HTTP_HOST} ^(www\.)?old-domain\.com$ [NC]
RewriteRule ^(.*)$ http://www.new-domain.com/$1 [R=301,L]