Lesson 1: know your route. Had I known the topography in advance I would've paced myself much better and possibly not had to stop and walk. The route was pretty much straight up hill for the first 2.5K and mostly downhill on the way back.
Lesson 2: Go sloooowwww . . . like, WAY slower than you think you should be. I thought I had learned this one during training, that the only way to go the distance is to pace really slowly, but in practice I guess my default pace is always starting out way too fast and burning out. I had to stop once to walk about 1 Km into it, and again briefly at 2K and 2.5K (top of hill for a water break). Still, I ran almost the entire way back down, and my final time was under 37 minutes. That's about 2 minutes better than my personal best, and 4 minutes ahead of my goal time. Which tells me I was going way too fast.
Lesson 3: Meta-lesson. I don't "learn" nearly as fast as I think I do, because I'll think I've learned something when I understand it intellectually, but it doesn't do me any good till I've learned it experientially. Until I knew what it felt like to apply lessons 1 & 2, above, I couldn't really apply them in the crunch.
But anyhow, I did it!!!! I finished the 5K in less than 37 minutes, and it was a glorious Family Event (both Nelson family and church family) for a good cause. Yaaayyy team! : )