Convert a 3-axis CNC Mill to a 3D Printer?

I have a couple of 3-axis CNC Mills, a larger SuperMax YCM-30, and a Sherline CNC-Mill. I was thinking of converting the Sherline to a 3D printer (I don't use it much anymore - was a great starter machine for this hobby).

Can anyone point me in the right direction of converting the Mill into a 3D printer?

Thanks!

Joe