Your information about the composition of the moon is 30 years out of date. He3 would be mined from the cold traps in permanently shadowed craters at the north and south poles of the moon. There it exists in extremely high concentrations, alongside other useful volatiles that together make up 40% of the surface material by weight.
“Refining” is a process as simple as shoveling it into a pressure container, heating it, and then letting dissipatively cool back to ambient temperature, collecting the other volatiles as they condense out. What’s left is a mix of inert gasses, including He3.
There is no data on 3He at the poles. The area there is small anyway.
The concentration of 3He on the moon in general is such that simply heating regolith without heat recycling and separation of fines would use more energy than the 3He would yield if fused.
“Refining” is a process as simple as shoveling it into a pressure container, heating it, and then letting dissipatively cool back to ambient temperature, collecting the other volatiles as they condense out. What’s left is a mix of inert gasses, including He3.