Before you think about opening up your own microwave, you should know that microwaves contain high voltage capacitors that will seriously shock or kill you even when they are unplugged. I knew a guy who got thrown across the room and was in serious condition for months. He didn't even touch anything, but he was wearing a wedding band and his hand got too close. Microwaves are serious business.
That said, I HATE the UI on my microwave & would love to fix it. Do people really eat that much popcorn that it deserves it's own button??? For me, I want exactly 3 controls: a time wheel, power up/down & a start button. Hit start for a quick minute, twice for 2 minutes, etc.