I've got a garmin 70s that came with my boat that I'm thinking of selling. The unit was used but the transducer was not(my buddy bought the unit new, didn't realize it didn't come with transducer mounting bracket. Only used as gps) Anyways, I have the unit used, but complete. Box, paperwork, 70s head unit, power cable, transducer, and the transducer mount. What is it worth? I haven't seen a lot of info about this unit.