First things first - drain and clean the fuel tank. Moisture in the tank will destroy a fuel injector quicker than the Bama man can wreck the economy. Blow out all the fuel lines including the return lines. Clean the fuel filter housing thoroughly then replace the element. Change the engine oil/filter and with the injectors loose (preferably out) turn the engine over about ten complete revolutions. Why? Have to knock the fuel injection pump return springs loose (this is a mechanical system) then re-install everything, pre-heat then crank for no more than 5 seconds at a time. Once it starts LISTEN for loose connecting rods - it will sound like a beating noise similar to those banger cars at intersections with the bass max'd out. If, and only if, you can't get the 'ol girl started on plain diesel try an ether based product with upper cylinder lube included - stay away from propane! Cylinder head won't take the added compression from the propane mixing with the diesel fuel. Kaboom and you'll be pinning a head. Concerning the PTO coupler - personally I'd stay away from spraying anything until heat has been applied. You are going to have enough problems with flash ignition of solidified grease/debris without adding a flammable penetrating oil onto the coupler.