Older husband syndrome

My husband is 7 years older than me, in good physical health now, but that won't last forever.
He's also a bit of a hypochondriac who assumes that any ailment is a dire one. I think that's a characteristic more common in men, but he's the only one I've ever been this intimate with for this long (almost 20 years), so that generalization is something of a guess.
My overall health seems really fine, but I have an underlying heart condition that means it all could take a serious turn for the worst in short order.
However, this post is about the back-of-my-mind anxiety that I'll have to be his caregiver in the coming years. I love him, of course, and want to help make his life easier and more comfortable. But I'm not exactly the nursing type, and have had not a moment's training in caring for someone who is chronically ill.
I guess, you get the training you need when the time comes?
At least one of my friends is married to a man 14 years older than she is, and I have an aunt who's been married for 30 years to a man almost 20 years YOUNGER than her. (At least in her case, the physically stronger person -- the younger man -- is likely to become the caregiver to his older wife.)
These age differences don't mean much when you're young or middle aged, but as old age creeps along.....well, it brings a new set of circumstances.
By the way, a recent issue (dated April 7) of New York magazine has some interesting stories and features about being old in New York City. Much if not most of it applies to being old in any city. Or maybe anywhere.