Finally had a chance to walk yesterday. Skipped the monitor, since I didn't want the kind of positive feedback that seems to lead to pushing it too hard. (I still have to get some professional advice on that.) But I walked for an hour -- up the hill and twice around the pond -- and didn't get cramps. So I must have done something right for a change.
Things I've learned: stretch, start out slowly, take small steps. Apparently years of sitting cause your leg muscles to shorten. Taking smaller steps means that they don't get overstretched. And I'm finally (I think) figuring out how to stretch properly: you have to remember to fully relax the muscle you're trying to stretch. That's hard.
I don't appear to have gained weight over the weekend, though I haven't lost any, either. I have gained about three pounds in the three weeks or so since I started getting leg cramps to the point where I couldn't walk regularly. So I'm glad to be getting back to it.