It is software, and will use CPU power, I would recommend a hardware raid controller such as THIS. Although it is expensive, it is much cheaper than other hardware controllers, and will let you really see the performance of your RAID
No problem, although you say you have no money left, I was thinking if you bought one more hard drive you could do a 0+1 array, also called RAID 10 sometimes. This would take all the parity calculations away.
I think the safest and easiest thing is to reformat. Since you will have the same capacity you maybe able to migrate it using the nforce raid software, but I wouldn't try it.
