I've owned 4 B-K's since 1990, and have never had any problem with the automatic damper, nor have I ever heard of one failing.
If your combustor were to go out (highly unlikely) you can still use the stove without a problem. You would burn a bit more wood, but it will function fine until you get a replacement. Figure on replacing it in 4 or 5 seasons, although it will work longer than that, just not as well.
If the glass were to break, yes, you would have a problem. The only reason it would break would be if you really went out of your way to break it. While not fragile, if you slammed the door shut on a piece of wood poking out of the fire box, or threw cold water on it while the stove is cooking along, yes, it might break, but it is going to need a lot of help.
Replacement parts are not difficult to come by, especially if you have an internet connection.
I replace the door gasket yearly, just because it is easy to do, but it is not a requirement.
There are thousands of these stoves in service, if they were fragile, unreliable or difficult to keep in order, you would definately hear about it on the net.
I just ordered a replacement combustor from Firecat, it arrived a week later. I could have gotten it sooner, but didn't care to pay for the express service. If I can get a part for a 19 year old stove that fast, you have nothing to worry about.
Congrats on picking a great stove, it will serve you well for many years. You could not have picked a better stove for sole source of heat.