I believe the previous post reply is confusing the 870 Ejector with the the Extractor and spring.
The extractor is in the bolt and the spring is behind it. The Ejector is the strip of spring steel that is riveted to the inside of the receiver.
The extractor can be replaced easily with a precision screw driver blade wedged between the extractor and the plunger that sits on the spring. Just press down on the plunger into the bolt and hold pressure
on it while with your thumb and forefinger of your other hand, jsut work the extractor out and pop in a new one. Takes about all of 5 seconds once you've done it a few times.
The 870 and older generation 1100s use the same extractor. The 11-87 and current generation 1100s (which are really 1100/11-87 hybrids) use a thicker extractor (30/1000ths") thicker .