If I replace the cam belt sensor will the EM light automatically go out or will it need resetting. Plus,do I need to remove cam belt to replace sensor?
Yes, the light will go out if the problem is fixed.
If it is the x18xe engine (pretty sure it will be) the cam belt does not need to be touched but you will have to remove the cambelt cover.
Buy or borrow the Haynes workshop manual for your car, costs about £20 from Halfords etc, or try charity shops etc.
It has full instructions with pics and tech data to help you do loads of maintenance and repair jobs, I buy one for every car I buy.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.