Glow Plug question

[76EBHorse]

Okay folks, I haven't seen my truck yet, accept in pictures(was my fathers day gift this year) but heres the deal. Wifey took it to my mechanic(guy works on all my vehicles) and he told her the check engine light is coming on becuase of a glow plug issue. He said it's either one of the glow plugs is going bad or the harness could possibly be faulty. Now like I said I take all my vehicles(2002 F-150, 1976 Bronco, 2007 Honda Pilot and now 2000 F-250) to him. I only go when something is beyond my capabilities or just don't feel like screwing with it.

Glow plugs seem fairly easy to me, pop the valve cover and bam there they are right? How do I narrow it down to which glow plug is giving me the problem or if it's the harness giving me problems. I'd like to take care of this when I get home from the sandbox, but would it just be worth letting my mechanic take care of it. Looking for any suggestions folks.

[ridiculously_necessary]

check this out, its what i used.
Troubleshooting GPR & GP's

then there is an R&R in the 7.3 repair/maintenence section. they are pretty straight forward. if you can repalce spark plugs you can probably replace glows.

[fragglerock2000]

might be the wiring harness under the cover i had it go on my 94 and 2000 and to cheak glow plug take test light hook clip to posative on battrey and the tip of test light to the tip of glow plug if light comes on they are good and if not you have to replace the plugs it dont come on

[NCHornet]

Follow the right up that was linked to above and you can quickly tell which GP's are bad. If the connectors look all crisp and burnt or corroded replace the harness. If I am going to replace 1 GP I might as well replace all eight. That's just my thinking.
Good Luck