1- remove the retaining ring Part # 30 on the Marlin parts manual.
2- Place a pin (paper clip will do - I used a red handled punch in the picture) so the hammer strut spring will not go flying.
3. Release the hammer by holding the hammer with your thumb and gently press the trigger and slowly let the hammer move to the fired position to release the hammer pressure on the spring. The hammer strut will stop at the installed paper clip.
Keep the pin in the hammer spring strut and remove as a unit from trigger housing.(see next post).