OK this is tricky so I won't send you to the manual.
To use the pads for the 60 just leave the midi channel field blank and leave it on drum.
to use the 60 pads to control the rack you need to set the midi channel, leave it set to drum, and hit the midi button, press number 2, then turn local off. Then you will only hear the rack samples.
Once the sequence is recorded, you need to change the track to midi so that upon playback you will only hear the rack samples, if you leave it on drum, the mpc samples will hit as well.
If you are using a controller, you set the midi channel to the rack and set the type to midi and the controller will play the samples without triggering the internal samples, which is probably the way the majority of their target market would work anyway.