To remove those stars, press them down and CUT OFF THE NUB at the bottom of the stem. DO NOT try to force it up through the retainer tabs.

If you get new star inserts from Pinball Resource you will need to shave off a tiny bit of the stem's thicker girth at the top of the stem. If you don't there is a good chance they will stick when pressed down.

You may be surprised how new brite white stars enhance a playfield. While you're poking around the stars, adjust the lamp underneath as close to the switch as you can get it without touching. Get that insert really glowing.