Replacing the mainspring housing is easy.
Remove the slide from the frame, remove the grips, lower the hammer (don't just pull the trigger and let it drop), lay the frame on your work area with the indented end of the Main Spring Housing Retaining Pin upward (that is the pin at the bottom of the frame/mainspring housing), with a 1/8" brass punch drift the pin out of the frame. There is a plunger in the MSH that holds the pin in place and you will have to thump the punch with something to get the pin out and in some cases your punch will be held by the plunger. In any case pull the pin out of the frame, pull your punch out of the frame, slide the MSH out of the frame and that part is done.
Is your new MSH complete with Mainspring Plunger, Mainspring, Mainspring Cap and Mainspring Cap Retaining Pin or do you have to remove those parts from the old housing?
Again it is an easy job.
Clamp the old MSH in a vise (padded jaws), with the top of the MSH upward and the base of it resting on a solid surface. Using a punch depress the MS Cap until you can remove the pin holding it in place (use a small punch - I use a long brad) by pushing the pin from the outside of the MSH. Remove the pin and, while maintaining control of the spring, cap etc let the spring extend to its full length. Remove the MSH from the vise, remove the parts from the MSH and set them aside. Place the new MSH in the padded jaws of the vise, slide the MS and MS Plunger into the MSH, place the MS Cap in the MS and depress the unit with your punch until the MS Cap Pin can be replaced. Make sure that the flanged end is flush with the interior face of the MSH.
Slide the new MSH into the frame, catching the hammer strut in the indent of the Mainspring Cap, and replace the Mainspring Housing Retaining Pin, rounded end going in first.
That should do it.
