I had a similar issue with the glowplugs in my suburban. I used a u-joint and an air ratchet and they came out without incident. Glow plugs are more difficult as carbon builds on the tip and they are much thinner then spark plugs and snap off in the pre injection chamber.

__________________
". . .back before accountants designed cars"

-Current Stable-
'78 MB 450SL-C 107.024.12.020783 #3840 <Kayleen>
'85 FORD F250 6.9L Diesel <Allison>
'98 Lexus ES300 <Rachel>
Long Gone...
'74 Chevy G10...........................'99 GMC Yukon 4X4
'83 Chevy Suburban 6.2 diesel .....'99 SAAB 9-5
'90 Mitsubishi Eclipse GS............. '01 Chevy Tahoe
'98 Nissan Altima .......................'02 MB ML320
'88 Chevy Suburban V2500 4X4 6.2 diesel