As for how to get the mag release out if you don't know how to do such now,

Use a pencil to push the mag release button all the way in (as far is it will go in, well past the face of the receiver), the turn the catch on the other side counter clockwise to unthread the catch form the button as you hold the button in.


When you reinstall the catch, make sure to flush the threaded part of the catch out with the face of the button (read is needed, turn the button 180* if you find that the catch seated is either 1/2 a turn either in or out from the threaded end being flush with the button face).