You say that you want to connect the 300 ohm resistor and a led to the input of the pic,
there is no problem with that with the pic but depending on what drives that input you may have a problem.
The 10k is used because any device will be able to feed that input resistance with 0.5mA and change the state of the pin,
on the other hand when you connect a low value resistor then the device that drives that pin may not be able to provide all tat current.
All that being said since you are just using a switch to provide the voltage to the pin you can use any resistor value,
the switch will not have a problem driving it.
Alex