If I am not wrong, CSC will help change your focusing screens for FREE !!! please call them to verify that. I ever brought a split-focusing screen from them at $60, and then I pass the screen and camera to the technician , they get it changed and then clean ( basic cleaning )on the spot for me. I get back my cam few minutes later only.
If you like to change the focusing screen, process to change is very simple, just a simple tweezer will do the job, difficult part is keep the screen free from dust and free from your own finger prints.
But, if you are like me, I don't mind focusing screen with little bit of dust... then I just change them myself lah...( these dust will not affect the picture quality because they are not in the direction of the image ).
please call CSC to check up more details .....