How can I clone a Dish Network drive?

I currently have a Western Digital MyBook Premier Edition 320gb drive (USB/Firewire) in use as an external hard drive on my Dish Network VIP 722 receiver. It has the proprietary format that Dish Network uses. I have purchased a 500gb USB drive to replace this drive so that I can use the WD drive as a backup drive for our computers (MacBook and iBook). I can move the movies currently archived on this drive one at a time back to the DVR, and then to the new drive. Only one of these drives can be hooked up to the DVR at a time, so this will be a rather tedious process. I would like to clone the current drive to the new drive, and then reformat the WD drive to use with the computers to avoid this tedious process. I've read that this can be done with Linux (which I know nothing about), but I don't have a clue how. Can this be done with Mac OS, perhaps Terminal? I consider myself fairly computer literate, but if this can be done, I will need step-by-step instructions as I know enough about Terminal to know that I shouldn't use it without them. Thanks for your help