Its not too difficult, but it is a pretty detail-oriented step through process. Deleting once the data is off the drives is easy. But you need to know how to transfer the data off and confirm its off. On the storage side, you need to know how to navigate the RAID card pre-boot setup interface. If you just pull drives and insert new ones the server will freak out and not do anything.
You need to delete old RAID group, add new drives, init them or flag as for use in RAID, then put them into a RIAD group that makes sense based on their capacity and usage profile. This means knowing when and why to pick RAID10, RAID6 as well as block size and read/write cache. Then you init the disk grounp, go back into VMware, find the unformatted volume and make that into your new Datastore.