[blue68f100]

It's easy on a guardian unit. If yhe unit has not been reset back to factory settings do so. May want to look to see if he had any addon keys. or OS updates on the unit prior.

Break the raid5 array if built.
Power down and remove all drives execpt #1
Power backup, hot swap a new drive into position 2.
Powerup, once up hot swap the remaining hd,
then build your new raid5.
Done

I took 5 hr to build the 4x400gig raid5 in my 4500 so 750's should be around 7 hrs.