In my opinion it is a good idea that you are re modelling your bathroom, mostly you will not face any problem and if so better consult to some professional as well before starting it.
A float switch is a device used to detect the level of liquid within a tank. The switch may be used in a pump, an indicator, an alarm, or other devices.For purchasing the best one search online and get it online.
In California mainly it is not necessary to get the license for plumber. In this country the contractor must have a license but the contractor itself must be a plumber.