yes, the gum should heal. it may not all grow back, but it should be ok. the stains on the teeth are just stains. the mercury tattoo is actual mercury that was put in your gums. they used it to prevent tooth decay from traveling up the tooth into the roots. as far as the stains, think of it like if you took some metal and set it on a painted white surface outside for many years. it would stain the paint. that is what happens to teeth over time.