What exactly does the Installation of EMG's require doing to your guitar. can someone explain this to me
Not anything really. All you'll need is new pots and someplace to put the battery, which may or may not require removing wood. Just depends on how tight the control cavity is.
You might night to route some space for the battery in the cavity, but that's all. Or route more space for the pickups if you have PAF/single coil sized pickups in the guitar.