The glow plugs can be changed DIY - I've done it, but it's a fiddly job with some nightmares!
The plugs are hard to see - they are close to the injectors at the front of the engine- but masked by the inlet manifold. You can't remove the manifold- or the cylinder head without removing the engine.
Use a 10mm 1/4 drive long reach socket, a 1/4 universal jount and a 1/4 to 2/3 adaptor. This can JUST be fitted to unscrew the glow plug after first removing the smaller supply connection nut and wiring. Make sure the glow plugs ARE faulty before going to all this fuss! Supply draw is around 45 amps for all 4 plugs in working order. Measuring resistance after removing the supply wire confirms an open circuit plug. Poor starting from cold is likely a likely indicator of 1 or more faulty plugs....
Andrerw Jones
October 2007