I currently have a 1TB hard drive installed in my computer, if I decided to add another one and put it in Raid 0, will I have to reinstall my OS? I think I probably would, but I just wanted to make sure here before I screw anything up. Thank you
Yes, you will need to rebuild from scratch. IMHO, if you are doing RAID 0 without a tape (or other) backup system for regular backups, you are an "accident waiting to happen". Data cannot be recovered if you lose one disk of a RAID 0. 2TB of data is a lot to lose.
No, not really. RAID0 isn't that important for performance of an OS drive. You'd be much better off buying an SSD and using that as your OS drive instead.