Removing and replacing hard disk

G man - if you returned the disk for a warranty replacement, it is unlikely that you will get your disk back. Instead you will get a refurbished disk that has no data and no partitions and the hour counter has been reset to 0. I have never gotten a Hitachi refurbished drive, but with Seagate the label has a green border and plainly states it is a refurbished drive. Just hot add it as mdgm has said and let the system do it's thing.

While it is gone, you may want to update you backup (which of course you have) to make sure that at least all your critical/important data (financial records, photos, etc) are backed up if not all you data. This is just in case you encounter a problem during the resync process. The resync process puts a lot of strain on the drives since it is constant file access for 6 or more hours, and if the other drive is showing any weakness it could fail during this time. While not common, this has been know to happen and then you have the dreaded dual HD failure. It is always better to have a backup and not need it than the reverse.