I think a bit of clarification is at hand here from reading some of the posts. It's not about one big pond of frozen water they were testing, it was how much water per unit of lunar material there is. When the impact happened, they measured not only how much water, but how much other materials were ejected as well. The point being, the higher the concentration of water / lunar material, the easier (and cheaper) to extract water from the surface. Imagine robotic vehicles scraping material from the surface and processing it (by heating it to melt and evaporate the water), where it would then be collected and stored. There's no frozen lakes with astronauts cutting out huge blocks of ice similar to the old school pre-refrigeration days where huge chunks of ice were cut from frozen lakes and stored underground for later usage (over the spring, summer and fall months). All the excitement is about the ratio of water to non-water materials in the measurements taken from the impactor. Apparently, the water to non-water ratio was quite high, making everyone happy. As far a how to power everything, my guess would be either some sort of nuclear reactor setup on the moon, or possibly a solar collector array concentrating the heat of the sun on a single point to heat water (of which there's plenty!), to run a steam turbine to generate electricity similar to systems that already exist here on earth.
