Is there a service manual or service codes available to get into the MyGig setting for Video/Nav/Radio etc?

Not just the users manual but a real servcie manual to toggle things on or off.

 

http://mofv.com/mygig/

You should find pretty much anything you want to know on the forums on that site. There is a service menu in MyGIG, - it's a three button combination (that I can't remember at the moment) to get into it. Be careful, though, because you can mess things up pretty bad once you're in the service menus.