Jon:
I'm sorry to hear about your brother.
MS is different for everyone, and every person with MS handles it differently. A while back, I was at the Cleveland Clinic Mellon Center, a hospital just for MS patients. I talked with one MS patient, a girl in her early thirties. She was doing exercises, and when they called her name, she ran to the front desk. Right after that, I met another girl in her early thirties, who was on a gurney, totally paralyzed. She couldn't move her head to look at me. So that's the range of MS: from almost no symptoms, to all symptoms, in their most severe form.
So far, your brother is lucky. Who knows what his future holds for him. The odds are really good that he'll never be in a wheelchair. MS can progress very rapidly, and then stop just as suddenly. MS can progress very slowly for a whole lifetime. No one knows how it's going to affect any individual.
I treat my MS like it's a joke, because everything in my life has to be funny, it's always been that way for me.
Other MSers don't think it's funny at all. Some (50% of all MS patients) are in depression at some point after diagnosis. Some want out. 20% of Dr. Kerkovian's (Dr. Death) assisted suicides had MS. I don't know the percentage of MSers who commit suicide, but it's higher than normal.
I can tell you one thing that bothers everyone with MS. To a casual observer, it may appear that the MSer displays his symptoms in varying degrees of severity. The MSer can be apparently devastated one day, and then on top of the world the next. That's actually exactly what happens. You have good days and bad days. One day you can hardly stand up, and the next day you can walk. To a really unsympathetic observer, it looks like the MSer is faking the disease. Of course, nothing could be further from the truth. To be burdened with the disease, and then to have some closed minded, (usually able bodied), person tell you that you're not really ill, or that you could cure everything if you really wanted to, usually stretches a friendship beyond repair. The effect is considerably worse if the observer is a relative.
If your brother has been diagnosed as having MS, he's got it. You simply cannot tell him what you would do if you were in his place. You are not in his place. Even he doesn't know what he's going to do in the future.
You say that you're confused about how to approach the subject with him? Welcome to the club. I've not met anyone who knows what to do in this situation. The only thing that you can do is offer him support when he needs it.
I wish your brother the best of luck in the future. I firmly believe that MS will be cured in the future, and that the effects will be reversible. See http://www.geocities.com/msthoughts/ on the internet.
Speedy