If it is truly a D9200 then it will not need an isolation transformer and assuming you are in the USA you should be able to plug into an outlet directly, though you may have to make or buy a proper cord, IIRC Bob Roberts sells the cord or I have seen them on ebay.
It's been a while since I've worked with one, but a D9200 is capable of displaying any VGA signal directly, it is a tri sync monitor, but you may have to change cable settings on the chassis, then you could always just hook up any modern PC with a VGA port and get a picture that way
This image may help you to verify the settings for cga/ega/vga cable positions
http://easymamecab.mameworld.info/files/d9200.jpgit also indicates where power cord wired could be installed with the proper colors.