I've used Garmin-they are good bits of kit and I have wanted to get parts repaired in the past. Forget it- believe me its cheaper to buy a new one and also you get the reliability with a guarantee of performance. If its built in then you have to strip it out and re-lay a new one. Make sure the transponder is securely fixed in a good position otherwise you will get "ghosting". Keep water away from the connections-thats how mine got damaged