Compaq ProLiant RAID 5 & NW4.11

We have a Compaq ProLiant 5500 running NetWare 4.11, it currently has 7 x 4.3GB in a RAID 5 array. We are planning on replacing the 4.3 drives with 9GB drives. As I am not that familiar with Compaq hardware I would like to know the best/quickest wayof achieving this with minimum disruption to the users and (obviously) no loss of data!

Any help is greatly appreciated.