You'll need to loosen the inserts in order to put them back in their correct position...

The first method would be to try and "tap" the insert out using a dowel or socket. Find a dowel or socket slightly smaller than the insert and lightly tap the insert from the underside of the playfield. You'll need to be very careful using this technique, because if you tap too hard, it could crack the insert. The glues they used on inserts in 1950s and 1960s machines degraded over time, so this tap method should work on this era of insert...

The second method would be to heat the insert with a heat gun and then try to tap out the insert.

The third method, if the other methods didn't work, would be to "cut out" the insert using a fine blade knife or X-acto blade type knife. This method will usually cause slight damage to the insert hole and it will need to be repaired with some type of glue filler or wood filler, and some paint touch up...

I usually use Elmer's white glue to secure the inserts. You can use a straight edge or ruler to position the inserts so they're level with the playfield...