System Restore from MBR to GPT

T310 Server
H700 Controller
4 ea. 450GB SAS  15K drives in a RAID-5
SBS 2008

I want to expand it by installing 2, 3TB SAS drives in a mirror, which would require changing to GPT.   How would I go about restoring the system to GPT?

If later I decided to add two more drives in a mirror, and move the data partition from the original virtual disk to the new one, would that mess up Windows?

Thanks!