You do not say what boiler,
BUT. I assume that you have a problem with hot water system. How do you know it needs descaling? Might be something else causing your problem.
Without dismantling the system, You would need to take covers off at minimum. You would then need to disconect the hot water inlet and outlet. Then set up a system to be able to pour a descaler into the heat exchanger, so that it comes out of the other port. Not forgetting that some need a time to work. BUT some need a special descaller. So what is the the heat exchanger made of, otherwise it will corrode the heat exchanger. Cause more damage. Lots of things that you have not mentioned. Easy way. Well.
SD, November 2012
