Yes, I just did it. It is a real PITA.
On mine the hole that held it in was elongated and was about to break.
Here is how I did it. You will have to judge for yourself if you think you can do it.
0. Go to Sears and get an AMERICAN made 1/16" pin punch. If you get a cheapo chinese one it will break.
1. Make sure it is empty, mag removed. Double check it is empty again.
2. Remove slide stop, and slide assembly.
3. Remove grips (4 screws). Once you remove the grips do NOT TOUCH the thumb safety! There is a spring below that thumb safety and if you move it the spring will fly out and the plunger will beam up into outer space. They are no longer available and your gun will be a useless paper weight.
5. Remove the mag release. This step is not necessary, but makes it a bit easier later. You just press in the mag release and turn the little screw until it clicks and then you can easily pull the whole assembly out.
6. Use your 1/16" pin punch and hammer out the top pin above the trigger. If your gun is blued and you are not careful you will damage the blue and you are looking at a refinish. Hit the pin from the right side of the pistol. It is in there very tight!
7. Remove the trigger assembly. Be VERY careful not to bend the little bar. If you do bend it you cannot get the part anymore and the gun becomes a paper weight. You will have to use three hands and lift up on the trigger to flip it up into position that you can lift the assembly out thru the top or mag well. Take your time here.
8. Use your 1/16 pin punch to remove the pin from the middle of the plastic trigger. There is a spring inside the trigger that holds in that bar and the spring is behind that.
9. Install the spring in the new trigger. Using three hands, compress the spring with a punch, insert the bar and punch the pin back in. Make sure your bar is oriented properly. before you tap the pin in. It may help to use a punch as a guide to hold the spring and bar in place while trying to insert the pin. Again do not bend the bar - else you have a nice paper weight. Make sure the spring action is smooth and the bar can move up and down without binding. There is also a little peice that goes up thru a grove that moves the bar up and down when the slide is moved back and forth. Make sure that peice is still in before you put the trigger assembly in place.
10. Reinstall the trigger assembly into the frame. Do not bend the bar. Else you have a paperwight...
11. You will need three hands and have to hold the trigger assembly in and use your 1/16 punch as a guide to line up the holes. You will have to push up on the trigger - rotate it and push up on the bar slightly to get everything to line up.
12. Tap the pin in a little - just enough to test.
13. Make sure the bar enguages the sear. Test that the trigger will make the hammer fall - careful - do not let the hammer drop (since the slide is not installed).
14. When statisfied, tap the pin all the way home.
15. Reinstall mag release, grips, slide.
16. Test function.
One mine, I had a problem where the trigger would not enguage the slide. I have to bend it so that when I squeezed the trigger, it would go bang.
Also, I guess I bent it too much, plus the spring was not smooth enough, so my Mustang did not fire correctly. I oiled the spring and readjusted the bar. But this does not seem to usally be the case. The alum trigger is supposed to drop right in.