Here's what I did.
1) Lower your TTL value for the domain you are switching IP's for.
2) Login to your (mt) account, setup the domains. Set up the mysql database on (mt).
3) Backup your database from Godaddy and import the sql files to the new database.
4) On your Godaddy wordpress installation update the wp-config files with your (mt) database info... that way you can still keep blogging during the transition.
... wait a day... take a break, drink some coffee.
5) Make a complete copy of your wordpress install from Godaddy over to Media Temple.
6) After that is all setup make sure the (mt) version is working. Media temple gives you an alternative access url to see your site before it goes live.
7) Login to your registrar and update the nameservers... to ns1.mediatemple.net and ns2.mediatemple.net
It shouldn't take too long to resolve considering that you lowered your TTL.
In any case if it does take long your site will still be up running on the mediatemple db.
... after a few hours or so do a tracert to your site to make sure it's pointing to media temple.