One can learn a lot from doing things wrong and having to fix it.
I'd pull the head and fix the threads if I had any intention of keeping that motor, as I personally think it's way to risky for someone who has never done this before to try it.
He'll end up with a big score in a cylinder wall from one little mistake, or have to replace the head anyway from a failed rethread attempt because of the screwy angles.
I know for a fact that the grease works for retaining the metal cut by the thread tool, but I'd still be in there with a magnet afterwards no matter what.
