Over the course of almost two years, I have made all of my changes to the twenty ten parent theme. I knew nothing about child themes, attempted to make one with little success. I am now being scared that not making updates is dangerous and I can lose all my work - just did a full backup of my theme today.
How would I go about make a child theme after I already made major changes to all the files of the twenty ten theme?
Please be very very specific because I am totally lost when it comes to this.