Most likely the root canal will be done in one visit, depending on the level of infecion in the tooth. My guess is you are seeing an endodontist, which is a dentist who specializes in root canals. Not all dentists use the gel you are talking about, but most keep it on hand for patients who request it, so just ask. Your general dentist will know whether or not the crown needs to be replaced. It just depends on what all is going on underneath it. Some dentists do allow friends, relative, etc. back, but not all. As far as I know, there is no one really allowed back in the op but staff and patient, but not all ofices follow this. Good luck to you and I hope this helps.