I am 68, live in Connecticut, and I've improved my conditioning greatly over the past five years by doing a lot of what's been suggested here, by keeping at it. I went from getting winded going up slight hills in my lowest gear to never getting winded even going up long steep hills and riding 150 miles a week.

On suggestion I would add is to get a basic, inexpensive cycling computer, one that records your speed and average speed, and for little more money, your cadence and heart rate. You will continue to feel crummy going up hills for quite a while, but you will be encouraged and motivated as you see your average speed steadily improve over the same course.

Once you are assured, probably by a doctor, that you have no limiting heart issues, a heart-rate monitor will be very helpful to your conditioning. My performance improved greatly when I started riding with a heart-rate monitor, because what it showed me most often was that my heart rate was considerably below my red-line maximum and that I could increase my pace without worrying about keeling over.

Anyhow, you deserve huge credit for wanting to do this.