My condolences to the owner! LOL.. ugh, that is exactly why I haven't replaced mine. As long as I have 2 or 3 good ones, and it starts... we're good! LOL
Dale
I have a little 3/8ths drive impact ratchet. It's exactly like this one, without the MAC branding (I bought it straight from the manufacturer in Japan).
Mac Tools Online Store - 3/8" Mini Impact Air Ratchet
With the air adjustment turned all the way down, a deep 8mm impact socket, and a three inch extension, not a heck of a lot of torque spikes transfer to the glow plug. And that's what you want. Put it on, let it go
tic tic tic tic tic for about ten seconds, then ziiiiing!, out comes the glow plug, undamaged. It's not strong enough to break it with the air turned down, but it shocks it enough to ease off the tension.
I also use an induction heater to heat up the glow plug for a few seconds before attempting, but those things cost around $500.