The 9/40/357 models use the typical S&W solid extractor pin. (The .45 uses a roll pin which was adopted in order to meet a perceived military spec when S&W was preparing to submit the M&P 45 in the anticipated, and then suspended, military pistol trials.)
They're removed top-to-bottom, but are very hard to remove. Like the 3rd gen guns, the extractor pins are installed with a press during factory fitting & assembly. Armorers have to do it the harder, old-fashioned way.
Even S&W armorers are told that it's really only recommended to remove them for repair purpose, though. Some experience is recommended, as well, since you really don't want to have the punch slip off the pin and wallow the top of the slide around the pin hole, or mangle the pin during removal or re-installation.
Usually a 'starter' punch is used to break them loose (and a 4 oz ball peen hammer), and then once freed they can be removed out the bottom of the slide with a straight stank 1/16" pin punch. (More than one armorer has 'created' an extra starter punch when bending/breaking a 1/16" Starrett pin punch.
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We were told in the M&P armorer class that the pins are mostly in the slides tighter than in the traditional model 3rd gen pistols, too.
It's not easy. I know another armorer who's very experienced with removing/replacing extractor pins in 3rd gen guns, and he broke a couple of pin punches trying to break M&P extractor pins loose. I haven't had any reason to remove an extractor in a M&P except in the class, and those guns were relatively easy because of all the times the pins had been removed and re-installed by armorer students.
The pins are installed bottom-to-top, in reverse order of removal.
Did you damage an extractor? If you're not familiar with removing S&W's pinned extractors it might be best to have it done by the factory, or else by a licensed gunsmith familiar with S&W pistols.