Wirelessly posted (WP7 Beta Tester: Mozilla/4.0 (compatible; MSIE 7.0; Windows Phone OS 7.0; Trident/3.1; IEMobile/7.0; HTC; HD7))
As far as I know, it won't change the SIM by flashing roms. As far as the code, just tell them you're going overseas on business
. (They usually just give it, unlike sprint)