Grow a RAID 5 array

I have an HP BL480C blade with 4 72Gb disks. The system is running ESX 3.0.1 and hosts 4 virtual machines. I need more space for the VMs and was wondering if I could swap out the disks (72Gb) for bigger (142Gb) ones, grow the RAID 5 array, increase the datastore and add the space to the VMs?

I know I can hot swap the hardware, no problems there. It's how to grwo the RAID 5 array on a 2.4 kernel I don't know about. Also growing the datastore is an unknown to me.

Any advice is welcome.

Thanks.