Uh oh! This brings back a terrible, terrible, terrible memory... 6 years ago, I owned a 1990 Ford F-250 4x4 which I purchased new. The damn thing (and I say damn because this thing was troublesome) only had 43,000kms in 1997 because of the terrible gas mileage it got (351 V8 auto & 4x4 = 12MPG) Anyways, driving to work one day, (wife needed the car) the engine suddenly got extremely loud. Because of the rush I was in, I brought it to the dealer and left it there. They called me the next day and told me that a spark plug had broken and only the threaded part remained in the head. Ugh, that doesn't sound good I thought to myself... Sure enough, when they tried to replace the rest of them, they were breaking in the same way! I told them to stop after the 3rd one because my bill was already at $400. So, (this is the part you are probably interested in) I took the truck home and tackled the rest of them myself. This is what I had to do to accomplish the job: I had to heat the area around the spark plug hole with a torch. Once the head was red hot, I inserted an "easy out" tool (available at most auto parts retailers) into the hole and tried to remove the remainder of the plug that way. This often had to be repeated because it didn't want to budge. Eventually it came out though. It took me about 5 hours to do 5 plugs. The mechanic told me that it's not the mileage that matters on plugs, it's the age. In my case the plugs had rusted out and became weak. I never dreamed of replacing my plugs at 43,000kms but now I am more careful about the condition of my plugs.
Chad
Fortunately i was able to slowly twist them and force them out. 
