See Haynes manual for your model of Diesel engine and refer to Fuel and exhaust systems section. Seems you may need a torque wrench of sorts to tighten again. But don't overtighten!
Disconnect battery earth and glow plug relay
(On my car this is a small black box clamped to chassis nr battery)
Disconnect feed wire from bus bar
Unscrew terminal nut from each plug
Remove nuts, washers and bus bar
Clean around plug seats then unscrew and remove them
When refitting apply some anti-seize compound to threads
Screw into place and tighten to specified torque
Refit bus bar, washers and nuts
Reconnect the feed wire and battery earth lead
Easier than it sounds I guess.
Paul Grant, January 2005
