Just my two penneth here.
Sometimes i've found by removing the securing screw it should in theory just lift off. This isn't always the case. If your unlucky enough to have a baseplate that has some corrosion around the top crankcase half it will put up a fight. If this is the case with yours then what i do in this instance is to strip down as much as possible all of the crankcase so you're left with the baseplate and top crankcase half together. I then use a hydraulic press (carefully) to push out the crankcase half from the baseplate. No fuss, easy as you like, no distortion and best of all you get to keep the skin on your knuckles.