Mercedes Benz repair: glo plug changing, glo plugs, glow plug

Question
how do you change the glo plugs on a 1984 mercedes 300sd turbo diesel 3.0 5 cyl. they foul evy 10-15 thousand miles and creat hard starting first start of the day only.

Answer
Glow plugs do not foul, but they do fail.
All you need is in the following three links.

Glow plug testing.
http://www.mercedesshop.com/shopforum/showthread.php3?t=104547&page=1&pp=15

Glow Plug Relay
http://www.mercedesshop.com/shopforum/showthread.php3?t=122826

wont start for anything!
http://www.mercedesshop.com/shopforum/showthread.php3?t=104222