Where and how do you change the glow plugs on a 97 F250 turbo diesel?

the glow plugs are located inside the the valve covers on the engine' the wire harness goes thru the cover gaskets.so this is a major job.if you break a gasket while removing, they cost about $70 , each to replace. you also need special tools to remove glow plugs. it is much easier and safer to take the truck to a reputable diesel mechanic.