I think this is the first question I can actually help with since joining! Normally I'm the guy asking the questions.
Anyway, when I bought my DM, the seller taught me how to remove and reinstall the back box. We needed to remove it to get it up his steps and then left it off to get it down mine. It wasn't difficult, but did take a little time. Just make sure you take a marker and label each and every connector with the corresponding number before disconnecting.
Once you get everything disconnected, you just feed both harnesses out of the back box, unscrew the hinges, remove the big bolt and lift off the box. There is one harness (at least in my game) that is self contained in the back box, but we removed it anyway. It's very difficult to determine which one it is with all the wires running around in there.
Just take your time, label everything and you'll be fine. I wouldn't hesitate to do it again by myself and I know very little about these things. I'm assuming that this is game specific, so I don't know how mine compares to yours.