Well, I am back from Mont St. Michel and I can tell you that I did make it to the top. Not, however, with some difficulty. From the start to the veranda is 8o meters high. There is a steep incline for about 200 yards before the stairs start. There are a series of steps approximately 15-20 at a time before you get to the final group of stairs.
There are about 60 to 80 steps at this point. Climbing 5 stories did help but what I needed to do and didn't was practice walking the steep incline. When you walk this incline you are bent over at the waist it is that steep. I suggest future elder people build this into their exercise regiment. The climb was worth the effort.