Emu XL-7 & MP-7 User's Group

Is it possible to make your own drum kits with the included samples?  What 
about editing the existing ones?  There's a whole keyboard worth of 
instruments mapped out in each one, but still only 4 layers to edit.  How 
do you know which drum samples are in each layer?  Is it possible to swap 
samples within the existing kits for other XL-7 samples?

Sorry so many questions, but I just got my XL-7 last week, got a lot of 
catching up to do :)

rEalm