I just peeked in your blog, good for you to find a low impact activity to improve your health. Given your health concerns I think more gears would help, you can learn to spin up hills and not put as much strain on your body. If you like the feel of flat bars you have a lot of options or you can even convert a road bike to different bars. Something to think about so you don't have quite as difficult time on hills. Of course some people ride with one gear so with time, patience and practice your gears will serve you fine if you cannot afford a different bike or simply do not want one.
Also, you should have the bike shop teach you how to change a flat. It was very empowering when I learned because it can temporarily ruin a ride but once it is fixed I can keep moving. I won't lie it is a pain in the butt to change one but it is some times part of cycling. Keep riding and tell us about your journey, we love to hear it!
Amanda
2011 Specialized Epic Comp 29er | Specialized Phenom | "Marie Laveau"
2007 Cannondale Synapse Carbon Road | Selle Italia Lady Gel Flow | "Miranda"
You don't have to be great to get started, but you do have to get started to be great. -Lee J. Colan