Rebuilding a site using wordpress – how to manage transfer

I’m helping a friend to rebuild his website using WordPress as a content manager. There’s a quite a lot of data on the site and he wants to rebuild the pages using WP and then transfer his domain name. He also wants to move to a new service provider.

I’d be grateful for any advice on how to manage the transfer. If we set up the pages initially using the (numerical) IP address the service provider will allocate, all the posts and pages will, I assume, be relative to that numerical address. On the final site we’d prefer it if the page and post references were relative to the (alphabetical) domain name of the site. Is there an easy way to do this without having to set up a new media library and go back and change all the hyperlinks in the initial version of the site?