OK.... Well, I just did it !!
No problems at all... AND, If anyone read my last call for help about the disks degrading after a short time, HD lights no longer working, NAS reverting to factory for no reason, etc..... I checked the Seagate site this morning and the ST320005N4A1AS-RK drive pdf info file states it is good for "highend/gaming computers and RAID arrays" so I breathed easier as I had a feeling it was a 4k sector drive!
The new unit is on FW1.08 and seems to be AOK. I think I will call d-link for an RMA for my other unit...