Replacing the hammer spring can be a little tricky, the first thing you need to do is look at the spring and make sure that you install the new one correctly, (speaking from experience). You will need to make a slave pin slightly smaller than the hammer pin so you can keep everything in alignment while you re-install the hammer pin, a brazing rod works well for this. Then all you have to do is get the spring squeezed back into the hammer recess and hold it there while you re-install the pin. Three hands would be a real asset here! After the first few times it gets a little easier. Good Luck!