Can anyone tell me how to remove the lens from my M frame. I am trying, but don't want to break them.

You pull/swing down the lense.  

Grab the frame in between your index finger and thumb of your weak hand.  Grab the lenses, right above the nose piece with your strong hand.  Swing the lenses away from the frame.  Stop when you feel resistance at the sides,  Should only be about 1/2" +/- away from the frame.

Pull one lens "foot" out of the frame.  Pull the other lens "foot" out of the frame.



Those little tabs are locked in the sides of the frame with pressure.  They will crack if you over swing the lenses from the frame.

+1

Middle first...then one side at a time.  They go back in in reverse.  One side then the other then the middle.

Good Luck