AGoyette:
I'm guessing that you lost the little plunger.... Apex can probably supply one for you, or you can send them the sear assembly and they'll put the newer plunger & spring in for you. (I forget the cost - figure about $20. You can ship the thing FedEx or UPS to get insurance, but don't need to call it a firearm.) There are two sizes of that little plunger. The original S&W sear spring and plunger are nearly microscopic. No idea what they were thinking.... Adding the updated Apex sear tended to make the sear reset iffy, meaning that the gun wouldn't cock during recoil. S&W slipstreamed the upgrade to a new, larger plunger and spring, and Apex started making those available (for a price

) to anybody who asked. The larger one won't fail....
(The originals seem to have varying reliability.)
IAC, trying to swap the spring (there's a new one in the DCAEK kit) is a "plastic bag" operation when you're dealing with the large plunger and spring, and not a bad idea with the older one. I lost one, too....
About a year ago, I decided to clean a 1911, and managed to launch the "button" that holds the recoil spring in place. Somehow, I got a couple of wrong ones from Brownells, and ended up deciding to bubba one I had here. About the time I started looking for a drill bit to clean up the job, I happened to look in the top area of the toolbox on the bench, and there it was. HOW that "button" (it's called a "plug") got up there - 2' or so higher than where the gun was when it went flying, and about a foot away - I don't know.... It's feeling much better now....
My wife's barely allowed in the office/workshop. She likes to throw things away, and drives me nuts about "why can't you throw this away?" when she finds something that even remotely looks like trash.
Clear devotee of "toss it on Monday so you can buy a new one on Friday."
There IS a disk under the rear sight, on top of the drop safety plunger spring. You really can live without that, but it's not likely you'll get it right, and that trashes the drop safety plunger spring.... The good news there is that you can fudge it with a little bit of very thin steel. No such luck for the sear plunger.... It does kind of look like a little blob of solder, though

- but is pretty clearly a machined part.
Regards,