Nice price on a good unit with very low hours. If we needed another one, I'd be on this like a duck on a bug.
If you have not used one of these...with these units, all you do is load the "BOB" data collection software into a laptop, plug the mag and a GPS sensor into the laptop's USB ports, make sure everything is talking to each other and start magging. The SeaSpy does require a 24V DC power source. (We use a pair of marine deep cycle batteries in series but the SeaSpy uses very little power.)