Switching RAID 0 to RAID 1 on brand new Dell Precision Tower 3620

I ordered a 3620 with 2 hard drives configured for RAID 0. It has already shipped. I realize now that I made a mistake and should have ordered the RAID 1 configuration. I realize this will reduce my total drive capacity.

Also, I'm planning on adding a 3rd HDD that I do not wanted to be included in the RAID. Any help on switching RAID levels and adding the 3rd drive would be appreciated. I'm expecting the machine to arrive tomorrow.

Thanks.