Loosen the screw  on the side of the grip , but before pulling it completely out, push it in to pop out the grip panel  on the opposite side. Be careful not to lose the small pin  behind the grip panel.
With the panels removed, push out the grip retaining pin .
With the retaining pin removed, slide the grip down.
With the grip removed, you have access to the hammer strut  and mainspring .
Note - The hammer has not been removed. This revolver has a bobbed hammer (the hammer does not have a spur). Sorry if the picture is misleading.
Cock the hammer  or pull the trigger  half way to expose a pin hole at the bottom of the hammer strut. Insert a paper clip or the pin from behind the grip panel into the pin hole at the bottom end of the hammer strut. Note the orientation of the hammer strut so you don't put it in backward during reassembly. You can refer back to the schematic or this picture if you forget.
Release the trigger and remove the hammer strut and mainspring.
Changing The Mainspring
This is the time to change the mainspring , if desired. Skip this step if you're not changing the mainspring.
Note - Removing the mainspring from the hammer strut  can allow the spring to launch.
To remove the mainspring, place the rounded end of the hammer strut in a padded vise. Be careful not to damage the hammer strut with the vise. With the hammer strut between the tines of a fork, push the fork down on the mainspring seat  to compress the spring. While holding the spring down, remove the paper clip or pin and the mainspring seat. Carefully decompress the spring and remove it from the hammer strut. This is a good time to gently sand any rough edges on the hole in the center of the mainspring seat and the edges of the hammer strut where the mainspring seat slides up and down. Slide the new spring on the hammer strut. Reassembly is the reverse of disassembly.
The factory mainspring is 14 lbs. A 12 lb spring is recommended, however a 10 lb spring can be used with increased risk of light primer strikes.
Carefully sand rough spots on the edges of the hammer strut . Gently polish the rounded end of the hammer strut.
Pull the trigger to free the hammer pivot pin .
While holding the trigger back, remove the hammer pivot pin.
While holding the trigger back, pull the hammer free.