Last winter my 93' W250 shutdown on me twice due to fuel gelling. Both times the tempeture was 0 to +5 degrees. I would get about a mile and a half from the house when it would lose power,run rough then die. Both times I waited untill mid'day, temperature 25 to 30, changed fuel filter, restarted and ran with no futher problems. I'm thinking a bad fuel heater. Can anyone help with recomendations for checking the operation of, and removeal, repacement of the fuel heater.