I was waiting for a mailer to send my gun back but instead they sent me a repair assembly, which meant that I would have to remove some pins in the M&P 9.
I have no punches but guess what the tool in the grip works quite well to remove these pins. So I did not buy anything and then after watching a video on You Tube
Smith & Wesson M&P Complete Disassembly - YouTube
You really only need to take out the locking block to replace the slide stop but while you are at it you might as well take out the sear block and clean them as well.
It took me a while because I wanted S&W to do it all and have confidence in their work but it not really that hard!