Can you provide any information about how likely is it that a recently-diagnosed sufferer is to be able to lead a mostly-normal life?

Meniere's disease is tremendously variable. Some patients may find their symptoms can be brought under control just by careful dietary control, in which case they may not appear in the physicians office again for a long period. At the other extreme, others have incapacitating attacks which have to be brought under control by more aggressive therapy before a normal life can continue. Treatments are established on a case by case basis, depending on the patients symptoms, the patients attitude (whether they want conservative or aggressive therapy) and the physicians experience with the wide range of therapies available. Most physicians start with dietary manipulation (low salt) and diuretics, then step through more aggressive therapies as required. The goal, of course, is to set the therapy at a level which allows the patient to lead a mostly normal life. Until there is a "cure" for Meniere's, the physicians role is to reduce the severity of symptoms so that a normal or near-normal lifestyle can continue.