Has anyone replaced the original horns on their diesel (mine is an '82 240) with the metal Hella horns? Is it "difficult"? Suggestions? Also,I'm about to replace both fuel filters. Someone told me to fill the gas tank and then "bleed" the air. Is this true? If yes,how is it done? Again , is it "difficult"?? I realize "difficult" is relative,but I'd really appreciate some opinions from some of the seasoned vets of this great site. Thanks. Dave W.