Thanks for the tips. I had found a step-by-step tutorial on the internet, studied it for a week or so, bought the springs, talked to the guys in the shop (OHD) and went to work. The fact is that I'm having more trouble with my door alignment and corresponding adjustments to the opener than the spring replacement. The door is "bowed" and doesn't sit flat end-to-end, where the cables attach on the bottom. I've reinforced the door and solidly attached the cross-rails, which were only screwed in occasionally.
For all this talk of "professional" installations and such, I can see that my door would be in better shape if the installers had attached the bracing correctly. The shoddy install has shortened the door's life, but I'm determined to keep my wooden door for many more years.
I guess my final thoughts on the springs is that there is too much hype around the process and not enough clarity around what it's all about. It's kind of like not telling teenagers the consequences of having sex. You know people are going to mess with these springs, it's better to put a pictorial up there by the springs than to hope and pray no one loosens the set screws without holding back on the spring.