First, yes there is 3He on the Moon. It's present at about the one part per billion level. You have to heat the soil to about 700 degrees C to drive off the 3He -- that several megawatts per ton of heating dirt. To be charitable, let's assume that you use focusing mirrors to capture "free" solar thermal radiation. You then have to collect it, isotopically separate the 3He, cyrogenically freeze it, store it, and transport it back to Earth.
But when you get it home, then what? We haven't achieved D-T fusion above breakeven yet, let alone D-3He fusion (which is about an order of magnitude more difficult). Commercial fusion power is like the end of the rainbow -- it's always "just around the corner." So, you're stuck with several tons of 3He, which I guess is useful to fill balloon animals with.
A much more proactical way to get energy from the Moon is to make solar panels on the surface using local materials and lay out solar arrays on the surface. Then, beam the electrical power back to Earth using microwaves of lasers. Basically, the Solar Power satellite idea, without the enormous launch costs associated with that concept.
I'll just mention this, an old idea in the FR archives.
reduces power consumption on earth;
the nasty Kyoto agreement is mooted;
hastens development of space mineral resources;
more of earth's real estate may be zoned residential rather than heavy industry.