Truck won't start cold. I changed the relay and still no luck, I think it is the glo plugs, 103 thousand on the truck and they have never been changed. How hard are they to change? I have heard that out of eight probably six will break on me? Would I be better letting the dealer do it? Never worked on a diesel before other than changing that relay. oh, if I plug the truck in it starts right up? but doubles my electric bill!