I might get some voltage surges and would not like to fry my arduino, also its a good oportunity to use them for the first time. Can you help me out on how to choose the appropiate one?
You could put in a protection diode for that. Get a 5V Zener diode and connect it in parallel with the lower resistor. If a voltage higher than 5V appears at the resistor junction the diode will short it to ground.
If the resistors have large values (75k, 5k) then there'll hardly be any amps, it should be enough protection.