Many of the SE’s stock buttons are crap. Your better off replacing them with 30mm Sanwa or Seimitsu, Snap in or screw in does not matter on Mad Catz SE and TE sticks.
As for the Disconnects, take you time gently rock the plug back and forth till its released. you might need a flat head screw driver to loosen the disconnects first. I personally took needle nose pliers to grab on the disconnects to pull them free before, Be careful if you try the pliers approach. Worst case scenario, if you ruin the wiring harness, since you replacing the board, is to get new wire and quick disconnects. Disconnects are 10 cents each and wire is about 25 cents per foot more or less. Just make sure you order extra quantities of wire and Disconnects encase you mess up.