I knew that long term exposure to Muriatic (Pool) acid would do that. I haven't seen vinegar do that in any of my cleanings using it. Frankly I didn't think that it was a strong enough acid TO do that. Though I rarely leave something soaking more than overnight. I've always de-greased with purple cleaner, so I had not idea if the vinegar would or wouldn't work on grease.
The head gasket surface is probably OK once it's been cut. I'd be most worried about the drool tube holes leaking if their size has been altered and that the rocker shaft saddles are no longer in the right place for proper rocker geometry.
