About cab and end car, there is no problem at all. Just open the window in the bottom part, close to the front bogie, and insert the Kato decoder FL12. You don't need to remove any plastic part, normally used as a lights switch, like in DCC ready EMUs.
But when you take the motor car and open the window, don't try to insert the EM13 decoder, because it will not fit. If you try it, probably you will brake it or it will be very difficult to take out. So first of all you need to unclip the upper part of the body. After that, you can unclip also the lower grey part of the body to access the motor.
But stop!!! Don't try to insert the decoder yet!! This model has a dummy decoder that you must remove before. After using some of this decoders in different trains, I never found a dummy in the motor car before.
I don't know if it's it's easy to see the dummy, or may be that day I was really sleepy, but I didn't see it and I fought with the car until I inserted the deco, but then it was impossible to fit again the body.
Here you can see the dummy removed:
And finally the decoder properly fit in place:
And the N700 is ready to run in a digital layout: