Could We Terraform the Moon?

I've been reading much on space mining and utilizing the Moon as a spaceport for longer missions - primarily to Mars. What are th challenges and limitations of mining regolith on the Moon? What can be extracted from lunar regolith? And can we manufacture enough to create a permanent Moon base? How about using regolith in a 3D printer for robotic assisted construction?

Awesome idea! Never thought of it before...