...been taken out which tells you when a service is due. they still have the circuit board
will this affect any other warning lights and would it be easy to refit the circuit board. is this common

people generally tend to do it to remove the automated message constantly telling you that you should have a service.

On the old Golf is used to display IN02

Its annoying... but for a car THAT age, especially a bmw, its probably a nail anyway.

its up to you if u want it get it there wont be any affects from it not being there

This is what people have to do unless you want to pay BMW $100 to reset the light everytime you do your own oil change.

It will not effect any other systems.