Re: stuck vanity with water source up from the floor
A sawzall will do the job well. Cut carefully along both sides and between both pipes to free the cabinet. You can also shut off the water at the main, removed the valves and pull the cabinet.
To install the new cabinet, drill holes large enough to fit over the valves then install split ring escutcheons around the pipes to hide the holes. Another method would be to turn off the water at the main, remove the valves and cut smaller holes to fit the pipes. Once the cabinet is in place, reinstall the valves and turn the water back on.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!