It seems to me that if someone is offering to do you a favor for free(solder a tuner etc.) That if you take them up on it, you do so AT YOUR OWN RISK. You either accept it or you don't have them do it. If you need assurance that there is no risk to you, you will have to build it yourself. Even if you took it to an electronics repair facility to have it built they would not guarantee its function after construction. I think you're making a mountain out of a mole hill. It sounds like the bottom line is: If you are going to offer to build these for free you need to have the person that owns it provide you with a signed document stating that they send this to you AT THEIR OWN RISK and hold you harmless for any reason , period.