Nad M3 non repairable

Just sell it on Ebay as not working, as-is.  Somebody will buy it.  Then they will tell you they want their money back because it's not working.  
I do think an amplifier should last more than 10 years, but you're lucky to get that out of a car and people accept it as part of life.  

@uberwaltz - That part about the returns was tongue in cheek.  I once sold my father's destroyed ESL tonearm which I described as "rusty junk" and the buyer told me the base was cracked!  He didn't want his money back though.  But that's why I'm sort of turned off by selling things mail order.  People want to buy used at half price and then expect new with warranty.  That's why I always try to sell local.  Come, inspect, listen and then make your decision.