It's really not difficult, nor is it as taxing on your body as you might think. You do have to dress for the weather - wearing layers is important, particularly the right layers. And if you ride in snow or ice, there are other precautions you need to follow, such as route selection and making yourself more visible.
In my search for help with ideas on winter riding, I found a great tip sheet from the University of Kentucky, which you can download and print by clicking here. It may well be one of the best resources you'll find. I know it's a welcome addition to my bag of tricks.
See you on the road!