Porting Win32 driver to EM64T

I have an IA32 bit platform (EM64T)which is running under 32 bit
processor , I have a kernel mode driver working fine on Microsoft
Windows Server 2003 Enterprise edition( 32 bit), I have to port that
driver for Microsoft Windows Server 2003 Enterprise x64 Edition,

I have few queries

  1. Will there be major impact in driver code? And what all I may have to
    change?

  2. Do I have to build the driver on Microsoft Windows Server 2003
    Enterprise x64 Edition, or I can use the Windows 2003 64 bit build
    environment to build it .

Thanks and Regards

~Neer