The proper in-block heater will get the coolant and the block to 40-45C in 3 hours, even at 0F outside. It's a darn shame what that guy did. If he had more sense and pride he would have declined to do it any other way than in the block, which IMHO is the only correct way. As for removing the original plug without a breaker bar, you did not speak to anyone who has actually done it.

__________________
'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.