I don't know your circumstances, but are you sure you couldn't handle a "human-powered" mower? I push a reel-type mower once a week over an expanse of lawn totalling about the same square-footage as what you have and I look forward to the two hours of exercise I get. Mother Earth will thank you too: even a modern lawn mower engine spews 10 times the amount of smog-causing gases into the air as a car -- the figures are much worse for older or improperly tuned engines ( http://www.santacruzsentinel.com/archive/2003/November/29/local/stories/10local.htm ).
I think the first step is to have less yard. A garden maybe? Some trees that are mulched?
Next, I'm sick of the gas mowers. They are loud and they stink. I'm tired of trying to start them. If not a manual mower, at least consider an electric mower.