I think you are going to have more problems. The part I circled in red should be splined and the part that holds it that you think is a spring pin only stops the shaft from sliding off. I would start by first removing the PTO shaft I circled in green. From there turn the PTO shaft to see if you have a hole on the other side. If you do then you will need to drive out the spring pin and remove the part circled in red and see if the splines are intact.