You don't have to put an SX drive in gear to remove it. With the cover off and cable disconnected you can easily shift it in and out of gear by hand. Once you have the cover off you'll see how to disconnect the cable. On the right side of the drive is the cable housing retainer that you loosen to allow the drive to slide back away from the cable and cable housing.
When installing the drive, it's handy to have it in gear so when you're trying to line up the spline with the engine coupler, you can turn the prop so the spline turns to help with engagement.