How would I transfer a pine tree from a pot to "in-ground"?

When I was about seven we all received a pine tree seedling in a dixie cup on Arbor Day in grade school. I planted it in a small pot and over the years would increase the pot size. Cut to twenty-four years later, I have a BIG potted tree that stands about seven feet tall. Now the problem is that the wind keeps knocking it over and two small branches have snapped off because of this. I don’t want to harm the tree because it’s kinda special to me. Yet, I’m apprehensive about planting it in the ground for fear of killing it. Any one with a green thumb know how to make the transfer? Do I just dig a hole, put it in and hope for the best? Should I purchase a certain type of soil or is plain old backyard dirt ok? I’d like to give this tree some room to expand.