This is using find and -mtime in Centos Linux, it simply takes "n" (which is a day) as a number and you can specifiy a + or - to say older or less than a certain age.
# (show everything older than 1 day)
find . -mtime +1
........
Before we start I take no responsibility for this, you should have a backup and if you make a mistake during this process you could wipe out all of your data. So backup somewhere else before starting this as a precaution, or make sure it's data you could afford to lose.
The RAID 1 Setup (Hardware Wise)
I've already setup my 2 x 1TB (Seagate) drives with identical partitions, make sure your new hard drive (the empty one) is setup like your curr........