You do not have to disassemble your shotty for that replacement. I replaced my plastic button with a metal button a few months back. I will tell you this....You have to be careful and patient. Do not unscrew the screw with the gun upright. The safety mechanism will fall inside. This is the tricky part. This is going to sound funny but this how I did it. Lay on you back on the floor. Get someone to hold the gun upside down over you so you can get to the screw that holds the button on. Slowly unscrew the screw until completely out. Do not move the gun after this...the mechanism will fall into the housing. ( this happened to me) If this happens it becomes a crap shoot to get the mechanism back into the slot the right way. Aftew removing the screw, slowly replace the old button with the new one. Try not to put to much pressure on the mechanism while installing the screw. If done correctly this only should take a few minutes. If done incorrectly it might not get done with out taking the reciever apart. I took me about an hour only because the mechanism fell into the housing. I had to repeatly shake the gun ,while upside down until the mechanism fell into the slot. Luck plays a huge factor in doing this.
Good Luck,
Mak