On my Dells (640m & XPS 1710) if you plug in the Ethernet cable it simply takes over from the WiFi. I will sometimes disable the WiFi but don't always.
Check the AC Adapter that came with the laptop, most modern laptop adapters allow for input of voltages from 100-240. If it does all you need is a plug adapter for it. For other equipment you most likely need a 230 to 112 converter.