Do not remove the spring and pin. Disconnect it and insert a small allen wrench or pin to keep it together.

I got in the middle of this same job and ran out of talent. Had to load it up and take it to my local lawnmower store. Apparently the cable I had was replaced by an improved version.

Yeah..those are a pain in the butt. The replacement cable should come in a kit form with the new arm that connects to the transmission. To do the job (assuming you are converting to the new cable/arm), you have to drive the roll pin out and install the new arm..re-using the old torsion spring.