ipscchef,
I say +1 to what everyone has said here.....go for it.
However, I feel that I should mention some things that maybe you have or have not thought of.
First, if you want to do a comprehensive list of gunsmithing services, you WILL spend hours standing on your feet running a lathe and a mill.
Chambering and fitting barrels and doing various mill work will require you to stand and spend some time bent over.
There are certain jobs that you can do sitting down at the bench......polishing, trigger work, parts fitting, etc.
Whatever school you attend, you'll be an "apprentice" when you graduate, any school will really " only get your feet wet".
A school can not possibly show you or get you ready for all the work you may encounter.
If you intend on going into business for yourself, it takes time to gain a reputation and build a client base....so, if you are looking at this for any kind of substantial income, it probably won't happen for awhile.
Working for someone else is an option.....IF you find someone willing to work with you and not stick you on a lathe or mill all day and who is willing to consider your medical situation.
Depends on what you can find.
If your looking at this as a serious hobby no problem.... but if you are looking at making a living at it and recouping your investment in school and time etc., these are things you may want to think about.
I still say go for it, but just realize some of the facts.
Good Luck