I currently run a RAID 0 configuration, so there is one drive acting as a redundant to the other,
I hope you mean RAID 1. Or you don't have any redundancy, but twice the chance of failure.
plus for the sites I develop I keep a current copy on my system at the office, but I could do with some kind of offsite back-up for user data, MySQL database(s) and web space content. I'm no Linux guru, and not 100% sure what to do to solve this issue. But I guess whatever I do, I need to be able to restore the back to another dedicated server or VPS if mine fails. What do you guys suggest?
You could use Plesk's backup tools. We don't use those: we have built our own remote backup solution with a web interface which also keeps history and lets you download or restore specific files/folders. We offer this service for a monthly fee or we could setup a backup system on one of your servers and maintain that for you.