Raid-0 is a big risk as far as data loss goes, if one drive fails you loose everything. After the motherboard is replaced the system should continue to run from the drives you have without any data being lost. You could simply remove both of the drives before you send it for repair.
As far as I know, any back up software will see this Raid setup as one single drive so even if you create a back up you will not be able to restore it to the Raid set up, it will have to go onto one single drive.
To take a back up of the drives you would need to connect them both to another PC and use software like Acronis True Image. I must add that this is only a "may be" as I am not sure if this will work with a RAID-0 configuration when the drives are hooked up to another PC.