Plain white vinegar works wonders for cleaning a tank and equipment, just rinse very well! The ich is long gone but I would personally toss the old gravel just as a precaution. It's pain in the behind to clean dirty old gravel but if your up to the task, go right ahead!
Yeah I will get new gravel. Will a good rinse work too? Forgot to add that the tank is acrylic if it changes anything...