FIVE glow plugs, one for each cylinder. You'll see them on the driver's
side of the cylinder head, there's a wire connected to each of them.

Buy Bosch or Beru brand replacements each costs about $9 as I recall.

Tools are needed: a wrench to turn the glow plug in and out and a small
wrench, preferably a very small socket (to not drop and lose) to remove
the nut that attaches the wire to the plug.

The glow plugs screw out like spark plugs. Carbon will cause some
binding as they come out.
Before installing the new glow plug twirl a 1/4 inch metal drill in each
hole, just with your fingers, to cut the carbon deposits or the new plug
won't go into the cavity.

Some are easy and others, especially the one behind the oil filter are
difficult to access.

Wear double latex gloves because there are lots of edges that will
scrape your hands.

DIY owner will need two to three hours to do this the first time.

Be sure all the nuts that attach the wires are snug or the Glow Plug
Lamp will soon be flashing!