HP Smart Array P420i RAID 5 HDD and Volume Expansion

Hello,
I have at one of my customers a HP Proliant ML310e Gen 8 with a HP Smart Array P420i  2gb Cache configured with RAID 5,   3 x 1TB Hard Drives.  this server has a 5 Drives bay.
Their systems database is growing in size at a really fast pace, and soon I'll have to replace the drives, My question is: What is the easiest path to replace the hard drive and how do I go about it and configuring? 

I've read on some forums people saying just replace one drive at a time, let it resync, then once all the drives are replaced, then increase the volume size,.  is this something that can be done on the P420i? 

Thank for the help and advice.