Creating a safe testing environment (with domain?)

Hi there,

I am looking at moving over my blog from WP.com to self-hosted via WP.org (with Dreamhost).

Current URL: http://wholesomecook.wordpress.com
Domain via GoDaddy: http://www.wholesome-cook.com (redirected to wp.com; expires August 2012)

Ideally, I’d like to:
– have no downtime,
– transfer the domain name from Go Daddy to Dreamhost and set it up as my primary domain for self hosted, while:
+ I test 2 themes for the purpose of the wp.org blog;
+ both the wc.wp.com and w-c.com domains are pointing to the old blog on wp.com

Is that possible? Can I set up a TEST.com domain and then change it to wholesome-cook.com when I’m ready? How can I create a safe testing environment?

I’d like to have it mostly worked out before I import my WC blog’s content over.

Thanks for any help offered, I hope it’s not too confusing.