Since I started this thread, I've had a carpenter put up a backyard fence. I found that my perfect compromise between DIY and paying full bore for the job was to act as the carpenter's assistant. It saved me the cost of the second person, moved the job along faster (which I was paying for by the hour), gave me the opportunity to learn by observing, got me some outdoor time and exercise, and still kept me from tuckering myself out. Sounds pretty good to me.